On this page 8 sections
What is B7 bolts material?
Quick answer
- Grade
- B7
- Material
- Cr-Mo alloy steel (AISI 4140/4142/4145), quenched & tempered
- Matching nut
- A194 2H
- Typical use
- Process piping flanges (ASME B16.5 / B16.47)
Technical summary
- Grade
- B7
- Material
- Cr-Mo alloy steel (AISI 4140/4142/4145), quenched & tempered
- Matching nut
- A194 2H
- Dimensions
- ASME B18.31.2 (studs), B18.2.1 (bolts)
- Certificates
- EN 10204 3.1; 3.2 on request
What is the chemical composition of B7?
| Element | Limit (%) |
|---|---|
| C | 0.37 – 0.49 |
| Mn | 0.65 – 1.10 |
| P | 0.035 max |
| S | 0.040 max |
| Si | 0.15 – 0.35 |
| Cr | 0.75 – 1.20 |
| Mo | 0.15 – 0.25 |
What are the mechanical properties of B7?
| Size / class | Tensile | Yield | Elong. | R of A | Hardness |
|---|---|---|---|---|---|
| Up to 2½" (M64) | 860 MPa (125 ksi) | 720 MPa (105 ksi) | 16% | 50% | 321 HBW / 35 HRC |
| Over 2½" to 4" (M64–M100) | 795 MPa (115 ksi) | 655 MPa (95 ksi) | 16% | 50% | 321 HBW / 35 HRC |
| Over 4" to 7" (M100–M180) | 690 MPa (100 ksi) | 515 MPa (75 ksi) | 18% | 50% | 321 HBW / 35 HRC |
Where are B7 bolts used?
- Process piping flanges (ASME B16.5 / B16.47)
- Refinery, petrochemical and power-plant equipment
- Valves, pumps and compressors
- Heat-exchanger channel covers
Selecting bolting for your joint
Bolting must suit the joint's temperature, pressure, environment and gasket. Coatings change the friction factor, so tightening torque must be recalculated. For sour service, hardness-controlled grades (B7M / 2HM) apply under NACE MR0175 / ISO 15156. See the bolting selection guide and flange types & classes.
What to include in your enquiry
- Grade and specification
- Diameter × length and thread series (UNC / 8UN / metric)
- Nuts and washers per bolt
- Coating and colour
- Quantity per size, or your flange schedule
- Certificates (3.1 / 3.2) and tests
Frequently asked questions
Which nut is used with A193 B7?
ASTM A194 Grade 2H heavy hex nuts.
What is the tensile strength of B7 studs?
860 MPa (125 ksi) minimum up to 2½", 795 MPa over 2½" to 4", and 690 MPa over 4" to 7".
Which standard covers B7?
ASTM A193 / ASME SA-193, with dimensions to the relevant ASME B18 standard.
Can the bolting be coated?
Yes: zinc, hot-dip galvanised, PTFE-based fluoropolymer or zinc-nickel coatings are available on request. Recalculate tightening torque for coated bolting.
Do you supply complete bolting sets for flange schedules?
Yes. Send your flange schedule (size, class, facing, quantity) and we will prepare the stud, nut and washer list.