Oct 6, 2026
What Is the Difference Between ER80S-B6 and ER80S-B8? Which One Should I Use?
ER80S-B6 and ER80S-B8 are both Cr-Mo welding wires, but they are designed for different material systems. So what is the difference, and can one replace the other?
ER80S-B6 vs ER80S-B8: The Quick Answer
The typical material-to-wire relationship is:
Base Metal | Typical Welding Wire |
|---|---|
P5 / T5 | ER80S-B6 |
P9 / T9 | ER80S-B8 |
The key point is that B6 and B8 have different alloy chemistry. They should not be treated as interchangeable simply because both are ER80S Cr-Mo welding wires.
The final consumable selection should follow the applicable material specification, WPS/PQR, code, and project requirements.
What Is the Main Difference Between B6 and B8?
The main difference is weld-metal chemistry, particularly the chromium and molybdenum alloy system.
ER80S-B8 is designed with a higher chromium level than ER80S-B6, making it suitable for higher-chromium Cr-Mo materials such as P9/T9.
This chemistry difference is important because the welding consumable needs to provide suitable weld-metal composition and properties for the base material and intended service.
Therefore, selecting B8 simply because it contains more alloying elements is not the correct approach. The consumable should be matched to the base-metal grade and qualified welding procedure.
Which Wire Matches P5 and P9 Steel?
For a straightforward selection:
P5/T5 → ER80S-B6 P9/T9 → ER80S-B8
This material-to-consumable relationship is more useful than choosing a wire based only on tensile strength.
For an actual project, also check whether the WPS/PQR and applicable code specify a particular AWS classification.
Can ER80S-B6 Replace ER80S-B8?
Do not assume that B6 can replace B8.
Changing from B8 to B6 changes the weld-metal chemistry and may affect the qualification basis of the welding procedure.
Potential issues include:
- Different chromium content
- Different weld-metal chemistry
- Different compatibility with the base material
- Changes to required qualification
- Project or code restrictions
The same principle applies in reverse: B8 should not automatically replace B6.
If substitution is being considered, the change should be evaluated against the applicable code, project specification, and qualified WPS/PQR.
Why Can't I Simply Choose the Higher-Alloy Wire?
More alloying does not automatically mean a welding wire is better.
For Cr-Mo steels, the objective is to achieve the required combination of:
Base Metal → Weld-Metal Chemistry → Mechanical Properties → Service Requirements
A consumable with higher chromium may be appropriate for one material but unnecessary or unsuitable for another.
This is why material matching is more important than simply selecting the higher-alloy classification.
Which One Should I Use?
If you only need a quick selection:
For P5/T5: use ER80S-B6 as the typical classification.
For P9/T9: use ER80S-B8 as the typical classification.
If the project requires a substitution, do not make the change based only on nominal tensile strength. Check the WPS/PQR, applicable code, material specification, and customer requirements first.
FAQ
Is ER80S-B6 the same as ER80S-B8?
No. They are different Cr-Mo welding wire classifications with different alloy chemistry and typical base-metal applications.
Can ER80S-B6 replace ER80S-B8?
Not automatically. B6 and B8 have different weld-metal chemistry, so substitution should be evaluated and qualified according to the applicable requirements.
Which welding wire is used for P5 steel?
ER80S-B6 is the typical solid welding wire classification associated with P5/T5 Cr-Mo steel.
Which welding wire is used for P9 steel?
ER80S-B8 is the typical solid welding wire classification associated with P9/T9 Cr-Mo steel.
Conclusion
The main difference between ER80S-B6 and ER80S-B8 is their alloy chemistry and material compatibility.
For a quick selection:
P5/T5 → ER80S-B6 P9/T9 → ER80S-B8
They should not be considered interchangeable simply because both are Cr-Mo welding wires. For any substitution, follow the applicable WPS/PQR, code, material specification, and project requirements.
