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Quick answer
Quick answer: ASTM A193 B7 strength by diameter
Minimum tensile and yield strength and maximum hardness for each A193 B7 diameter range, read from the full mechanical-property table below. Pair B7 studs with A194 2H heavy hex nuts.
| Diameter | Tensile strength min | Yield strength min | Hardness max | Inquiry |
|---|---|---|---|---|
| Up to 2-1/2 in | 125 ksi (862 MPa) | 105 ksi (724 MPa) | 321 HBW / 35 HRC | Quote this size |
| Over 2-1/2 to 4 in | 115 ksi (793 MPa) | 95 ksi (655 MPa) | 321 HBW / 35 HRC | Quote this size |
| Over 4 to 7 in | 100 ksi (690 MPa) | 75 ksi (517 MPa) | 321 HBW / 35 HRC | Quote this size |
Sourcing these sizes? PTFE coated stud bolts guide Stud bolt supplier
A193 B7 mechanical properties
Minimum values per ASTM A193 Grade B7 (quenched and tempered chromium-molybdenum alloy steel). Strength steps down as diameter increases because larger sections harden less through their thickness.
| Diameter | Tensile strength min | Yield strength min | Elongation min | Reduction of area min | Hardness max | Inquiry |
|---|---|---|---|---|---|---|
| Up to 2-1/2 in | 125 ksi (862 MPa) | 105 ksi (724 MPa) | 16% | 50% | 321 HBW / 35 HRC | Quote this size |
| Over 2-1/2 to 4 in | 115 ksi (793 MPa) | 95 ksi (655 MPa) | 16% | 50% | 321 HBW / 35 HRC | Quote this size |
| Over 4 to 7 in | 100 ksi (690 MPa) | 75 ksi (517 MPa) | 18% | 50% | 321 HBW / 35 HRC | Quote this size |
B7 vs B7M
B7M is the same alloy family with a much lower hardness limit, used where sour (H2S) service or hydrogen-assisted cracking is a concern. The lower hardness costs strength, so the two grades are not interchangeable on a design.
| A193 B7 | A193 B7M | Inquiry | |
|---|---|---|---|
| Max. hardness | 321 HBW / 35 HRC | 235 HBW / 99 HRB | Quote this size |
| Min. tensile (under 2-1/2 in) | 125 ksi | 100 ksi | Quote this size |
| Hardness testing | Sample testing per lot | Every piece hardness tested | Quote this size |
| Matching nut | A194 2H | A194 2HM | Quote this size |
| Typical use | General refinery, chemical and power flanges | Sour service, NACE MR0175 / ISO 15156 projects | Quote this size |
Stud thread sizes and matching A194 2H nuts
Sizes up to 1 in normally use UNC threads; 1-1/8 in and above use the 8UN series (8 threads per inch). Width across flats is for heavy hex nuts, which are larger and thicker than finished hex nuts of the same thread.
| Stud diameter | Thread | A194 2H heavy hex nut — width across flats | Inquiry |
|---|---|---|---|
| 1/2 in | 1/2-13 UNC | 7/8 in | Quote this size |
| 5/8 in | 5/8-11 UNC | 1-1/16 in | Quote this size |
| 3/4 in | 3/4-10 UNC | 1-1/4 in | Quote this size |
| 7/8 in | 7/8-9 UNC | 1-7/16 in | Quote this size |
| 1 in | 1-8 UNC | 1-5/8 in | Quote this size |
| 1-1/8 in | 1-1/8-8 UN | 1-13/16 in | Quote this size |
| 1-1/4 in | 1-1/4-8 UN | 2 in | Quote this size |
| 1-3/8 in | 1-3/8-8 UN | 2-3/16 in | Quote this size |
| 1-1/2 in | 1-1/2-8 UN | 2-3/8 in | Quote this size |
Typical stud bolts for ASME B16.5 raised-face flanges
Flange studs are ordered as sets: quantity, diameter and length per flange joint. The table shows typical nominal values for raised-face flanges with spiral-wound gaskets, allowing for two nuts and thread protrusion. Ring-joint flanges, thicker gaskets, spacers and hydraulic tensioning need longer studs, so always check the project bolting table.
| NPS | Class 150: qty × dia. × length | Class 300: qty × dia. × length | Inquiry |
|---|---|---|---|
| 1 | 4 × 1/2 in × 3 in | 4 × 5/8 in × 3-1/4 in | Quote this size |
| 2 | 4 × 5/8 in × 3-1/2 in | 8 × 5/8 in × 4 in | Quote this size |
| 3 | 4 × 5/8 in × 3-3/4 in | 8 × 3/4 in × 4-1/4 in | Quote this size |
| 4 | 8 × 5/8 in × 4 in | 8 × 3/4 in × 4-3/4 in | Quote this size |
| 6 | 8 × 3/4 in × 4-1/4 in | 12 × 3/4 in × 5 in | Quote this size |
| 8 | 8 × 3/4 in × 4-1/2 in | 12 × 7/8 in × 5-3/4 in | Quote this size |
| 10 | 12 × 7/8 in × 5 in | 16 × 1 in × 6-3/4 in | Quote this size |
| 12 | 12 × 7/8 in × 5-1/4 in | 16 × 1-1/8 in × 7-1/2 in | Quote this size |
Need these ASTM A193 Grade B7 sizes? Request a quote
- State how length is measured. Flange stud lengths are commonly quoted excluding the chamfered points; some buyers measure end to end. One line in the RFQ avoids a short-stud dispute.
- Order two A194 2H heavy hex nuts per stud, plus spares if the project calls for them.
Coatings: plain, PTFE, hot-dip galvanized
| Finish | Why it is chosen | Points to check | Inquiry |
|---|---|---|---|
| Plain / black oxide | Lowest cost; used indoors or where studs are replaced at each shutdown | Rusts quickly in humid or coastal plants | Quote this size |
| PTFE (fluoropolymer) coated | Corrosion protection plus easier removal; common on offshore and coastal sites | Colour, coating thickness and salt-spray requirement; coat studs and nuts together | Quote this size |
| Hot-dip galvanized | Thick zinc for outdoor and coastal exposure | Nuts must be overtapped; ask how high hardness parts are controlled for hydrogen embrittlement | Quote this size |
| Zinc plated | Mild indoor protection | Baking after plating for this hardness range | Quote this size |
Need these ASTM A193 Grade B7 sizes? Request a quote
- We can supply PTFE-coated A193 B7 studs and A194 2H nuts; state the colour and any coating specification in the RFQ.
- Coatings change the friction factor. If studs are tightened by torque, the torque table must match the coating.
How to specify A193 B7 studs in your RFQ
- Grade: A193 B7, or B7M for sour service, with the required edition if your specification names one.
- Diameter, thread series (UNC or 8UN) and length, and how length is measured.
- Nuts: A194 2H (or 2HM) heavy hex, quantity per stud.
- Finish: plain, PTFE coated (colour), hot-dip galvanized or zinc plated.
- Documents: EN 10204 3.1 inspection certificate, heat number traceability and marking on stud ends and nuts.
- Packing by flange set or by size, and labelling for site use.
Order these sizes from HEXVARO
Send your size list with grade, finish and quantity — we reply within 2 working hours with price, lead time and shipping terms.
- Reply: within 2 working hours
- MOQ: 500 pcs per specification
- Lead time: 10–15 days stock items
- Payment: T/T · L/C · PayPal
- Shipping ports: Tianjin · Ningbo · Shanghai · Shenzhen
- Incoterms: EXW · FOB · CFR · CIF · DAP
- Experience: Founder with 10+ years in the fastener industry
Frequently asked questions
What is the tensile strength of A193 B7?
125 ksi (862 MPa) minimum tensile and 105 ksi (724 MPa) minimum yield for diameters up to 2-1/2 in. From 2-1/2 to 4 in the minimums are 115 / 95 ksi, and from 4 to 7 in 100 / 75 ksi.
What nut goes with an A193 B7 stud?
ASTM A194 Grade 2H heavy hex nuts are the standard match for B7 studs. B7M studs are normally paired with 2HM nuts.
What is the difference between B7 and B7M?
B7M has a lower maximum hardness (235 HBW / 99 HRB vs 321 HBW / 35 HRC) for sour or hydrogen service, lower strength (100 ksi tensile), and every piece is hardness tested.
How many studs does a 4 inch Class 150 flange need?
Eight 5/8 in studs, typically about 4 in long for a raised-face flange with a spiral-wound gasket. Check the project bolting table for ring-joint or special gaskets.
Can A193 B7 studs be PTFE coated?
Yes. PTFE (fluoropolymer) coated B7 studs and 2H nuts are widely used in coastal and offshore plants. We can supply them coated; specify colour and coating requirements.
What is the MOQ for A193 B7 studs?
Reference MOQ is 500 pcs per specification. Stock sizes typically ship in 10–15 days and made-to-order sizes in 25–30 days, subject to quotation.
What is the tensile strength of an A193 B7 stud?
125 ksi (862 MPa) minimum for diameters up to 2-1/2 in, with 105 ksi (724 MPa) minimum yield. Larger diameters have lower minimums (see the table).
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