On this page 8 sections
What is B8M bolts material?
Quick answer
- Grade
- B8M
- Material
- Type 316 stainless steel, Class 1 or Class 2
- Matching nut
- A194 8M
- Typical use
- Marine and coastal equipment
Technical summary
- Grade
- B8M
- Material
- Type 316 stainless steel, Class 1 or Class 2
- Matching nut
- A194 8M
- 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 B8M?
| Element | Limit (%) |
|---|---|
| C | 0.08 max |
| Mn | 2.00 max |
| P | 0.045 max |
| S | 0.030 max |
| Si | 1.00 max |
| Cr | 16.0 – 18.0 |
| Ni | 10.0 – 14.0 |
| Mo | 2.00 – 3.00 |
What are the mechanical properties of B8M?
| Size / class | Tensile | Yield | Elong. | R of A | Hardness |
|---|---|---|---|---|---|
| Class 1 (all sizes) | 515 MPa (75 ksi) | 205 MPa (30 ksi) | 30% | 50% | 223 HBW / 96 HRB |
| Class 2 (up to ¾") | 760 MPa (110 ksi) | 655 MPa (95 ksi) | 15% | 45% | 321 HBW / 35 HRC |
Where are B8M bolts used?
- Marine and coastal equipment
- Chemical and pharmaceutical flanges
- Offshore utility systems
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
Is B8M the same as SS 316?
B8M is the ASTM A193 bolting designation for Type 316 stainless steel.
Which standard covers B8M?
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.