ER90S-B9 – wire and rod for 9Cr-1Mo-V steel (F91)
9Cr-1Mo filler metal modified with vanadium, niobium and nitrogen, for F91 steel (grade 91) in thermal power plants and supercritical steam lines.
Product forms and equivalents
| Process | Classification |
|---|---|
| TIG rod (GTAW) | ER90S-B9 |
| Solid MIG/MAG wire (GMAW) | ER90S-B9 |
| Covered electrode (SMAW) | E9015-B9 / E9016-B9 / E9018-B9 – AWS A5.5 |
| Flux-cored wire (FCAW) | E91T1-B9 – AWS A5.29* |
| Submerged arc wire (SAW) | EB9 + flux – AWS A5.23 |
| Designation | Value |
|---|---|
| AWS | ER90S-B9 |
| Specification | AWS A5.28/A5.28M / ASME SFA-5.28 |
| UNS | S50482 |
| Others | EN ISO 21952-A: W/G CrMo91*; AWS A5.28M: ER62S-B9 |
Chemical composition (%)
| Element | wt. % |
|---|---|
| C | 0.07 – 0.13 |
| Mn | ≤ 1.20 |
| Si | 0.15 – 0.50 |
| Cr | 8.00 – 10.50 |
| Mo | 0.85 – 1.20 |
| Ni | ≤ 0.80 |
| V | 0.15 – 0.30 |
| Nb | 0.02 – 0.10 |
| N | 0.03 – 0.07 |
| Al | ≤ 0.04 |
| Mn + Ni | ≤ 1.50* |
| P | ≤ 0.010 |
| S | ≤ 0.010 |
| Cu | ≤ 0.20 |
Properties of the deposited metal
| Property | Value |
|---|---|
| Tensile strength of deposited metal | ≥ 620 MPa (AWS minimum, after PWHT) |
| Yield strength | ≥ 410 MPa (AWS minimum, after PWHT)* |
| Elongation | ≥ 16 % (AWS minimum, after PWHT)* |
Materials welded with ER90S-B9
Why the composition differs from the base metal
It repeats the V, Nb and N of F91, but limits Mn + Ni. These two elements lower the Ac1 critical temperature of the bead; if it drops below the PWHT temperature, part of the bead re-austenitizes and forms fresh, untempered martensite. That is why AWS limits Mn + Ni to 1.50 % in the wire. The wire may have more Ni than F91, because nickel improves bead toughness, but the sum must stay below that limit so that Ac1 remains above the PWHT temperature.
Welding precautions
- Preheat of about 200 to 250 °C and maximum interpass around 300–350 °C.
- Before PWHT, let it cool below about 100 °C to complete the martensitic transformation.
- PWHT mandatory, typically 745 to 775 °C, without exceeding the Ac1 of the bead.
- TIG with pure argon; MIG/MAG with argon and 2–5 % O2 or up to 20 % CO2*. Clean, dry wire and bevel to limit hydrogen.
Frequently asked questions
What is ER90S-B9 used for?
9Cr-1Mo filler metal modified with vanadium, niobium and nitrogen, for F91 steel (grade 91) in thermal power plants and supercritical steam lines.
Why is the composition of ER90S-B9 different from the material it welds?
It repeats the V, Nb and N of F91, but limits Mn + Ni. These two elements lower the Ac1 critical temperature of the bead; if it drops below the PWHT temperature, part of the bead re-austenitizes and forms fresh, untempered martensite. That is why AWS limits Mn + Ni to 1.50 % in the wire. The wire may have more Ni than F91, because nickel improves bead toughness, but the sum must stay below that limit so that Ac1 remains above the PWHT temperature.
Which covered electrode corresponds to ER90S-B9?
E9015-B9 / E9016-B9 / E9018-B9 – AWS A5.5.
What precautions apply when welding with ER90S-B9?
Preheat of about 200 to 250 °C and maximum interpass around 300–350 °C. Before PWHT, let it cool below about 100 °C to complete the martensitic transformation. PWHT mandatory, typically 745 to 775 °C, without exceeding the Ac1 of the bead. TIG with pure argon; MIG/MAG with argon and 2–5 % O2 or up to 20 % CO2*. Clean, dry wire and bevel to limit hydrogen.
