Oct 6, 2026
What Welding Wire Should I Use for P11, P22, P5, P9, and P91 Steel?
What welding wire should you use for P11, P22, P5, P9 or P91 steel? Compare ER80S-B2, B3, B6, B8 and B9/B91 for Cr-Mo welding.
Choosing the right welding wire for Cr-Mo steel starts with the base-metal grade and chemistry, not simply the required tensile strength. P11, P22, P5, P9, and P91 belong to different Cr-Mo alloy systems and typically require different filler metals.
Welding Wire Selection for P11, P22, P5, P9 and P91
Base Steel | Cr-Mo System | Typical Welding Wire |
|---|---|---|
P11 / T11 | 1.25Cr-0.5Mo | ER80S-B2 |
P22 / T22 | 2.25Cr-1Mo | ER90S-B3 |
P5 / T5 | 5Cr-0.5Mo | ER80S-B6 |
P9 / T9 | 9Cr-1Mo | ER80S-B8 |
P91 / T91 | Modified 9Cr | ER90S-B9 / B91 |
These are typical material-to-filler-metal combinations. The final selection should be confirmed against the applicable specification, project requirements, and qualified WPS/PQR.
What Welding Wire Is Used for P11 Steel?
P11/T11 → ER80S-B2
P11 is a 1.25Cr-0.5Mo steel commonly used in boilers, high-temperature piping, heat exchangers, and power-generation equipment.
ER80S-B2 is a typical solid welding wire for applicable GTAW and GMAW applications. Its Cr-Mo chemistry is designed for applications where suitable weld-metal properties are required at elevated temperatures.
What Welding Wire Is Used for P22 Steel?
P22/T22 → ER90S-B3
P22 is a 2.25Cr-1Mo steel widely used in high-temperature piping, pressure equipment, and power-generation applications.
ER90S-B3 is a typical solid-wire choice for applicable welding procedures. B3 has a different Cr-Mo chemistry from B2, so ER80S-B2 should not automatically replace ER90S-B3 when welding P22.
The filler metal should be selected according to the required weld-metal properties and qualified welding procedure.
What Welding Wire Is Used for P5 Steel?
P5/T5 → ER80S-B6
P5 is a 5Cr-0.5Mo steel used in high-temperature piping, refinery, petrochemical, and pressure-equipment applications.
ER80S-B6 is a typical welding wire for compatible P5/T5 applications. Its higher chromium content distinguishes it from B2 and B3.
The important point is that a higher-alloy wire is not automatically a suitable substitute. The filler metal must match the required weld-metal chemistry and qualified procedure.
What Welding Wire Is Used for P9 Steel?
P9/T9 → ER80S-B8
P9 is a 9Cr-1Mo steel designed for demanding high-temperature service.
ER80S-B8 is a typical welding wire for compatible P9/T9 applications. Because B8 belongs to a higher-chromium alloy system, it should not be selected simply because it has a similar strength classification to another Cr-Mo wire.
What Welding Wire Is Used for P91 Steel?
P91/T91 → ER90S-B9 / B91
P91 is a modified 9Cr steel designed for high-temperature and creep-resistant service.
ER90S-B9 or the applicable B91 classification may be specified depending on the applicable standard and qualified welding procedure.
P91 welding requires careful control of preheat, interpass temperature, heat input, cooling, and PWHT. P91 should therefore not simply be treated as another P9 welding application.
Can One Welding Wire Replace Another?
Not automatically.
Although P11, P22, P5, P9, and P91 are all Cr-Mo steels, their alloy systems and required weld-metal properties are different:
P11 → B2
P22 → B3
P5 → B6
P9 → B8
P91 → B9/B91
For example, ER80S-B2 and ER90S-B3 may be used in similar high-temperature industries, but they are designed around different weld-metal chemistries.
When considering a substitution, check the base material, AWS classification, welding process, applicable code, service conditions, and qualified WPS/PQR.
Does Preheat or PWHT Affect Welding Wire Selection?
Yes.
Welding wire is only one part of the Cr-Mo welding procedure. Preheat, interpass temperature, heat input, cooling conditions, and post-weld heat treatment can affect weld-metal and HAZ properties.
The required parameters depend on the material grade, thickness, welding process, applicable code, and qualified procedure. Generic preheat or PWHT values should therefore not replace the project WPS/PQR.
FAQ
What welding wire should I use for P11 steel?
ER80S-B2 is a typical welding wire for P11/T11 steel, subject to the applicable specification and qualified WPS/PQR.
What welding wire should I use for P22 steel?
ER90S-B3 is a typical choice for P22/T22 steel in applicable GTAW/GMAW applications.
Can I use ER80S-B2 for P22 steel?
Do not assume it can replace ER90S-B3. P11 and P22 belong to different Cr-Mo alloy systems, so the filler metal should be verified against the applicable code and qualified welding procedure.
What welding wire is used for P91 steel?
ER90S-B9/B91 is associated with P91/T91 applications. Always verify the required classification against the applicable specification and WPS/PQR.
Quick Reference
If you only need the answer:
P11 → ER80S-B2
P22 → ER90S-B3
P5 → ER80S-B6
P9 → ER80S-B8
P91 → ER90S-B9/B91
The correct welding wire should be selected according to base-metal chemistry, welding process, service requirements, applicable standards, and qualified WPS/PQR—not simply by strength level.
