Heat-resistant Cr-Mo steels
FERVEO CMO 91B HD P2
covered electrode · stick electrodebasic coatingCatalogue only
also as: covered electrode · stick electrode
AWS class
E9018-B91 H4
EN ISO class
E CrMo91 B 42 H5
Tensile strength (Rm)
620 MPa
Classification
| AWS class | E9018-B91 H4 |
|---|---|
| EN ISO class | E CrMo91 B 42 H5 |
Purpose
- High-alloy, low-hydrogen basic electrode (H4), P91 grade (9% Cr–1% Mo–V–Nb, AWS E9018-B91 H4, EN ISO E CrMo91 B 42 H5) — for supercritical-cycle power-plant boilers.
Why it works
Vanadium and niobium added to the 9Cr-1Mo base (versus the FERVEO CMO 9 family, without V/Nb) form fine carbonitrides that give the P91 grade much higher creep strength than a conventional 9Cr-1Mo at the same temperature — the reason this grade is the standard in supercritical-cycle power-plant boilers. Its higher hardenability demands tighter preheat and interpass temperature control (200–315°C) than the rest of the family, to avoid cold cracking.
Fields of application
- Supercritical-cycle power-plant boilers and piping in P91 (T91) steel.
Chemical composition
| Element | Typical, % |
|---|---|
| C | 0.09 |
| V | 0.2 |
| Cr | 9 |
| Mn | 0.5 |
| Mo | 1 |
| Nb | 0.04 |
| Ni | 0.6 |
| Si | 0.2 |
Mechanical properties
| Tensile strength (Rm) | 620 MPa |
|---|---|
| Yield strength (Rp0.2) | 530 MPa |
| Elongation (A5) | 17 % |
| Impact energy (KV) | 47 J (20 °C) |
Process
| Polarity | DC± |
|---|---|
| Positions | PAflatPBhorizontal-verticalPChorizontalPDhorizontal-overheadPEoverheadPFvertical-up |
| Re-drying | 300–350 °C / ≥2 h |
| Heat treatment | 745-775°C / 2h / |
Sizes and part numbers
| Ø | Length | Current | Request |
|---|---|---|---|
| 2.5 mm | 350 mm | 80–110 A | |
| 3.2 mm | 350 mm | 110–140 A | |
| 4 mm | 350 mm | 140–190 A |
Cross-reference
| Replaces CROMOCORD 91 (Oerlikon) | Requires WPS validation |
| Replaces CROMOCORD 9M (Oerlikon) | Requires WPS validation |
Equivalence refers to the classification (AWS / EN ISO), not to product identity. In applications with a qualified procedure (WPS), validate the substitution before use.
Base metals
X10CrMoVNb 9-1A213 Gr. T91A 335 Gr. P91 (T91)A 139Gr.T91% 9-12 Cr typemartensitic stainless steels.
Advantages
- Much higher creep strength than a conventional 9Cr-1Mo (FERVEO CMO 9 family) at the same temperature, thanks to vanadium and niobium — the standard in supercritical-cycle plants.
Limitations
- Higher hardenability than the rest of the FERVEO CMO family — demands tighter preheat and interpass temperature control (200–315°C) to avoid cold cracking.
- Same P91 grade as FERVEO CMO 91B HD P2 15 — choosing between the two comes down to the AWS classification required by the qualified WPS, not a meaningful performance difference.