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
21CrMoV5-7 vs ASTM A193 Grade B8 (EN 10269 Cross-Reference)
21CrMoV5-7 (Werkstoff 1.7709) and ASTM A193 Grade B8 family (B8, B8M, B8C, B8T) are completely different alloy families. B8 family is austenitic stainless (304 / 316 / 321 / 347 base) for cryogenic to mid-temperature corrosion-resistant service; 21CrMoV5-7 is a Cr-Mo-V low-alloy bolting steel for high-temperature creep-resistant service. They are not interchangeable — different design intent, different mechanical envelopes.
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At a Glance
| 21CrMoV5-7 | ASTM A193 Grade B8 (304) | |
|---|---|---|
| Alloy class | Low-alloy Cr-Mo-V Q+T | Austenitic stainless (304 base) |
| Service envelope | 200 to 550 deg C | cryogenic to 540 deg C |
| Magnetic | Yes (ferritic-bainitic) | No (austenitic) |
| Corrosion resistance | Modest (Cr 1.20 to 1.50) | High (Cr 18 to 20, Ni 8 to 10) |
| Cost per kg | Mid (Cr-Mo-V alloy) | Higher (Ni-rich austenitic) |
Chemistry Comparison
| Element | 21CrMoV5-7 | ASTM A193 B8 (304) |
|---|---|---|
| C | 0.17 to 0.25 | 0.08 max |
| Cr | 1.20 to 1.50 | 18.0 to 20.0 |
| Ni | 0.60 max (residual) | 8.0 to 10.5 |
| Mo | 0.55 to 0.80 | none (B8M has 2.0 to 3.0) |
| V | 0.20 to 0.35 | none |
Mechanical Comparison
| Property | 21CrMoV5-7 | ASTM A193 B8 class 1 |
|---|---|---|
| Tensile (Rm) | 700 to 850 MPa | 515 MPa minimum |
| 0.2 percent proof (RT) | ≥550 MPa | ≥205 MPa |
| Corrosion service | Atmospheric only | Wet / chemical / marine |
When to Specify Which
Specify 21CrMoV5-7 for high-pressure / high-temperature steam, turbine and power-plant bolting where corrosion is not the failure mode. Specify ASTM A193 B8 family for chemical-process, marine, food-grade, or cryogenic bolting where corrosion resistance is the design driver. The two grades address different failure modes — choose by which is dominant in the application.
Form Availability
Both grades supplied in round bar and the full bolting form-factor range: stud bolts, hex bolts, heavy hex bolts, tap studs, nuts, washers and threaded rod.
Frequently Asked Questions
Q. Can I substitute B8 for 21CrMoV5-7 in a steam turbine?
No. B8 austenitic stainless has much lower yield strength (205 MPa vs 550 MPa minimum) and creep performance drops above 540 deg C. Steam-turbine casing flanges need the Cr-Mo-V yield and creep envelope.
Q. When would I choose B8 instead of 21CrMoV5-7?
When the bolted joint sees a corrosive environment (marine, chemical process, food-grade) and the temperature is below 540 deg C. The austenitic chromium-nickel chemistry resists corrosion; the Cr-Mo-V cannot.
Q. Are B8 stainless bolts non-magnetic?
Yes. Austenitic 304 / 316 stainless is non-magnetic in the solution-annealed condition. 21CrMoV5-7 is strongly magnetic (ferritic-bainitic Q+T microstructure).
Q. Do you supply ASTM A193 B8 bolting?
A193 B8 austenitic bolting ships from torqbolt.com separately as it is outside the 21crmov57.com scope. Contact for cross-grade procurement on mixed-spec projects.
Related Cross-References
More cross-references: vs ASTM A193 B16 · vs ASTM A193 B7 · vs 21CrMoV5-11 · vs 24CrMoV5-5 · vs Durehete 1055 · vs 20CDV5.7 (AFNOR) · vs 21HMF (Polish) · vs 42CrMo4. Back to the 21CrMoV5-7 Alloy Hub.
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