Heat Resistant & Cr-Mo
ER90S-B9 for P91 & T91
AWS A5.28 ER90S-B9 solid welding wire for P91, T91, F91 and compatible 9Cr-1Mo-V-Nb steels used in high-temperature and creep-resistant applications. ER90S-B9 is a 9% chromium, 1% molybdenum low-alloy welding wire designed for welding compatible heat-resistant steels used in demanding high-temperature service. Its controlled additions of vanadium, niobium and nitrogen support the required weld-metal properties for creep-resistant steel applications.
ER90S-B9 Welding Wire
ER90S-B9 is a legacy AWS A5.28 low-alloy welding wire classification associated with P91, T91 and other Grade 91 steels.
It belongs to the modified 9Cr-1Mo-V-Nb consumable system used for elevated-temperature and creep-resistant applications.
Important classification note: AWS A5.28/A5.28M:2020 added ER90S-B91 and replaced the former ER90S-B9 classification. ER90S-B9 therefore remains relevant when buyers search for legacy specifications, existing procedures, older documentation or replacement-compatible products.
Typical Grade 91 applications include:
- P91 and T91 welding
- Main steam piping
- High-temperature pressure piping
- Boiler and heat-transfer components
- Power-generation equipment
- Refinery and petrochemical equipment
- Other compatible Grade 91 components
Commercial ER90S-B9 products have historically been supplied in both GTAW/TIG and GMAW/MIG forms, depending on manufacturer and product specification.
ER90S-B9 at a Glance
Item | Details |
|---|---|
Legacy AWS Classification | ER90S-B9 |
Current Replacement Classification | ER90S-B91 |
AWS Specification | AWS A5.28 / ASME SFA-5.28 |
Product Type | Solid welding wire / TIG filler rod |
Alloy System | Modified 9Cr-1Mo-V-Nb |
Typical Materials | P91, T91, F91 and compatible Grade 91 steels |
Strength Class | ER90 |
Typical Processes | GMAW/MIG, GTAW/TIG |
Main Service | High-temperature / creep-resistant applications |
Typical Industries | Power generation, boilers, refinery and petrochemical |
Product Form | Spool / TIG rod |
Documentation | TDS / MTC / CoA according to requirements |
AWS currently lists A5.28/A5.28M:2026 as the specification for low-alloy steel electrodes and rods for gas-shielded welding processes.
Why Is ER90S-B9 Still Searched?
ER90S-B9 is important today mainly because older technical documents, specifications and product references may still use the B9 designation.
AWS A5.28/A5.28M:2020 changed the classification system by adding ER90S-B91 and replacing ER90S-B9.
This creates two common purchasing situations:
Existing B9 Specification
A customer may have an existing:
- WPS/PQR
- Welding procedure
- Equipment specification
- Engineering drawing
- Maintenance specification
- Material or welding record
that still identifies ER90S-B9.
New Procurement
A new project may specify ER90S-B91 instead.
Therefore, buyers should check the applicable edition of AWS/ASME requirements and the project documentation before treating B9 and B91 as equivalent classifications.
ER90S-B9 and the Grade 91 Material System
ER90S-B9 is associated with the modified 9Cr-1Mo-V-Nb Grade 91 consumable system.
Typical compatible materials include:
- ASTM A335 P91
- ASTM A213 T91
- ASTM A182 F91
- ASTM A387 Grade 91
- ASTM A336 F91
- Other compatible Grade 91 steels
Commercial product data identifies ER90S-B9 for P91/T91/F91 and describes it as a modified 9CrMo consumable containing controlled niobium, vanadium and nitrogen additions.
The important selection principle is:
Grade 91 base metal → compatible Grade 91 consumable → qualified welding procedure
ER90S-B9 Chemical Composition
ER90S-B9 is based on a modified 9Cr-1Mo-V-Nb alloy system.
Typical commercial chemistry may include approximately:
Element | Typical / Classification Concept |
|---|---|
C | Controlled |
Mn | Controlled |
Si | Controlled |
Cr | Approximately 9% |
Mo | Approximately 1% |
Ni | Controlled |
V | Controlled addition |
Nb | Controlled addition |
N | Controlled addition |
Cu | Controlled |
A Lincoln commercial ER90S-B9 product, for example, lists typical wire chemistry of approximately 8.9% Cr, 1.0% Mo, 0.20% V and 0.06% Nb, with additional controlled elements.
The exact chemistry should always be verified against the applicable specification and the actual MTC/CoA.
ER90S-B9 Mechanical Properties
ER90S-B9 belongs to the ER90 strength class.
Mechanical properties depend on:
- Welding process
- Shielding gas
- Heat input
- Welding parameters
- PWHT
- Test condition
Manufacturer-specific data can therefore differ significantly from simple classification minimums.
For example, one commercial ER90S-B9 TIG product reports typical post-PWHT values of approximately 500 MPa yield strength, 700 MPa tensile strength and 18% elongation, with impact performance reported at -20°C.
For procurement, use the actual TDS and MTC for the supplied product rather than treating a manufacturer's typical values as universal.
ER90S-B9 for P91 and T91
P91 Welding
ER90S-B9 welding wire for P91 steel is the main historical application associated with this classification.
Typical P91 applications include:
- Main steam piping
- Hot reheat piping
- High-temperature pressure piping
- Headers
- Boiler components
- Power-generation equipment
T91 Welding
ER90S-B9 is also associated with T91 tube applications, including:
- Boiler tubes
- Superheater components
- Reheater components
- High-temperature heat-transfer equipment
- Power-generation systems
The actual consumable selection should follow the applicable material specification and qualified WPS/PQR.
Where Was ER90S-B9 Used?
Commercial ER90S-B9 products have been positioned for demanding elevated-temperature applications.
Examples include:
Power Generation
- Main steam piping
- Power-generation plants
- Boiler components
- Turbine-related components
Refinery and Process Equipment
- Oil refinery equipment
- High-temperature process piping
- Pressure equipment
- Petrochemical process systems
Specialized High-Temperature Plants
Commercial product literature also identifies applications such as coal liquefaction and gasification plants.
For any specific project, suitability depends on the base material, service conditions, code and qualified welding procedure.
ER90S-B9 Welding Processes
GMAW / MIG
Historical ER90S-B9 products have been supplied as solid wire for GMAW/MIG applications.
Important variables include:
- Wire diameter
- Shielding gas
- Current
- Voltage
- Wire-feed speed
- Travel speed
- Heat input
Actual welding parameters must follow the applicable qualified WPS.
GTAW / TIG
ER90S-B9 is also documented as a TIG filler/rod for Grade 91 applications.
GTAW can be considered for:
- Pipe root passes
- Precision welding
- Critical joints
- Controlled deposition
Commercial product data includes TIG sizes such as 2.0, 2.4 and 3.2 mm for specific ER90S-B9 products.
P91 Welding Procedure: Preheat, Interpass and PWHT
Grade 91 welding requires control of the complete thermal cycle.
Important variables include:
Preheat → Interpass Control → Heat Input → Cooling → PWHT
Depending on the project, additional controls may include:
- Hydrogen control
- Hardness
- Cooling rate
- PWHT temperature
- Holding time
- Heating and cooling rate
A product webpage should not prescribe one universal P91 welding temperature because the applicable requirements depend on the material thickness, joint design, welding procedure and construction code.
Always follow the approved WPS/PQR and applicable code.
ER90S-B9 vs ER90S-B91
This is the most important comparison on the page.
| ER90S-B9 | ER90S-B91 |
|---|---|---|
Status | Legacy classification | Replacement classification |
Typical Material | P91 / T91 | P91 / T91 |
Alloy System | Modified 9Cr-1Mo-V-Nb | Grade 91 consumable system |
AWS A5.28:2020 | Replaced | Added |
Main Application | Grade 91 | Grade 91 |
Buyer Consideration | Existing specifications / legacy documents | Current project classification |
AWS A5.28/A5.28M:2020 explicitly states that ER90S-B91 replaced ER90S-B9.
Therefore:
Older / legacy specification → ER90S-B9
Replacement classification → ER90S-B91
Do not assume that a material certificate, WPS or project specification can be changed from B9 to B91 without checking the applicable code and qualification requirements.
ER90S-B9 vs ER80S-B8
| ER90S-B9 | ER80S-B8 |
|---|---|---|
Material System | Grade 91 | Grade 9 |
Typical Material | P91 / T91 | P9 / T9 |
Alloy System | Modified 9Cr-1Mo-V-Nb | 9Cr-1Mo |
Strength Class | ER90 | ER80 |
V / Nb | Controlled Grade 91 additions | Different alloy system |
Typical Service | High-temperature / creep | High-temperature |
Main Selection Factor | Grade 91 compatibility | Grade 9 compatibility |
P9/T9 → B8
P91/T91 → B9 / current B91
Similar chromium content does not mean the two consumables are interchangeable.
ER90S-B9 vs ER90S-B92
| ER90S-B9 | ER90S-B92 |
|---|---|---|
Typical Material | P91 / T91 | P92 / T92 |
Alloy System | Modified 9Cr-1Mo-V-Nb | Modified 9Cr-W-V-Nb |
Material System | Grade 91 | Grade 92 |
Typical Service | High-temperature / creep | High-temperature / creep |
Main Selection Factor | P91/T91 compatibility | P92/T92 compatibility |
Grade 91 → B91
Grade 92 → B92
ER90S-B9 vs ER90S-B3
| ER90S-B9 | ER90S-B3 |
|---|---|---|
Typical Material | P91 / T91 | P22 / T22 |
Alloy System | Modified 9Cr-1Mo-V-Nb | 2.25Cr-1Mo |
Strength Class | ER90 | ER90 |
Material System | Grade 91 | Grade 22 |
Typical Service | High-temperature / creep | High-temperature |
Typical Industries | Power generation | Boiler / refinery / process |
P22/T22 → B3
P91/T91 → B91 / legacy B9
How to Select an ER90S-B9 / B91 Product
Because B9 is a legacy classification, buyers should confirm the following before ordering:
1. Existing Specification
Does the drawing, WPS, PQR or purchase specification specifically require ER90S-B9?
2. Current Classification
Does the current project instead specify ER90S-B91?
3. Base Material
Is the material P91, T91, F91 or another compatible Grade 91 steel?
4. Welding Process
GMAW/MIG or GTAW/TIG?
5. Diameter
What diameter is required by the qualified procedure?
6. PWHT
What post-weld heat-treatment requirements apply?
7. Documentation
Is MTC, CoA, third-party inspection or additional traceability required?
8. Packaging
Spool, TIG rod or another packaging format?
Diameter and Packaging
Available diameter and packaging depend on the manufacturer, product form and welding process.
Commercial ER90S-B9 products have historically been available as:
- GMAW/MIG spools
- GTAW/TIG rods
- Different wire diameters
- Industrial packaging
- Project-specific packaging where available
For quotation, provide:
Classification + Base Material + Diameter + Welding Process + Quantity + Packaging
Quality and Technical Documents
For Grade 91 projects, buyers may request:
- Technical Data Sheet (TDS)
- Mill Test Certificate (MTC)
- Certificate of Analysis (CoA)
- Chemical composition
- Mechanical properties
- Impact test data where applicable
- Certificate of Conformity
- Packaging information
- Heat/batch traceability
- Project-specific documentation
For legacy B9 procurement, it is particularly important to confirm whether the customer requires the historical B9 designation or the replacement B91 classification.
Frequently Asked Questions
What is ER90S-B9 welding wire?
ER90S-B9 is a legacy AWS A5.28 low-alloy welding wire classification associated with modified Grade 91 steels such as P91 and T91.
Is ER90S-B9 still a current AWS classification?
ER90S-B9 was replaced by ER90S-B91 in AWS A5.28/A5.28M:2020. It may still appear in older specifications, documents and product references.
What is ER90S-B9 used for?
It is associated with Grade 91 applications including P91/T91 piping, boiler components, power-generation equipment and other high-temperature applications.
Is ER90S-B9 suitable for P91?
ER90S-B9 was designed for Grade 91 applications including P91, subject to the applicable specification and qualified welding procedure.
Is ER90S-B9 suitable for T91?
Yes, historical commercial product data identifies ER90S-B9 for T91 applications.
What replaced ER90S-B9?
ER90S-B91 replaced ER90S-B9 in AWS A5.28/A5.28M:2020.
What is the difference between ER90S-B9 and ER90S-B91?
They are associated with the same Grade 91 material system, but B91 is the replacement AWS classification for B9.
What is the difference between ER90S-B9 and ER80S-B8?
B9 is associated with modified Grade 91 P91/T91 steels, while B8 is associated with Grade 9 P9/T9 steels.
What is the difference between ER90S-B9 and ER90S-B92?
B9 is associated with Grade 91 P91/T91 steels, while B92 is associated with Grade 92 P92/T92 steels and a different modified 9Cr alloy system.
Can ER80S-B8 be used for P91?
Do not assume substitution. P91 requires a compatible Grade 91 consumable system and qualified welding procedure.
Does ER90S-B9 require PWHT?
P91/T91 welding requires procedure-specific control of PWHT and other thermal variables. Follow the approved WPS/PQR and applicable code.
Need ER90S-B9 or Its Replacement Classification?
Looking for ER90S-B9 welding wire for P91, T91, Grade 91 or legacy 9Cr-1Mo-V-Nb specifications?
If your project specifies the older B9 designation, send us:
AWS Classification · Base Material · Diameter · Welding Process · Application · Quantity · Certificate Requirements
We can also review whether the project documentation calls for ER90S-B9 or ER90S-B91.
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