What is the difference between P91 and P92 pipe fittings?

P92 (Grade 92, EN 1.4901, X10CrWMoVNb9-2) adds 1.5–2.0% W (tungsten) and reduces Mo to 0.30–0.60% compared to P91 (0.85–1.05% Mo, no W). The W addition strengthens the matrix at elevated temperatures via solid-solution strengthening, giving P92 approximately 15–20% higher allowable stress than P91 at 600°C and above. P92 also adds a trace of Boron (0.001–0.006%) which stabilises the grain boundary M23C6 carbides. P92 is used in ultra-supercritical (USC) and advanced USC steam plants where temperatures exceed P91's practical limit. Welding filler must be ER90S-B9M (W-bearing) — not the standard B9 used for P91.

What filler metal is used for welding P92?

P92 requires ER90S-B9M (GTAW) or E9015-B9 (SMAW) filler — the 'M' designation confirms the W-bearing composition matching the P92 base metal. Using standard ER90S-B9 (P91 filler) is not recommended for P92 as it lacks the W addition and will produce a diluted weld with lower elevated-temperature strength. PWHT at 750–780°C is mandatory. Preheat of 200–250°C is required and the joint must not be allowed to cool below preheat temperature during welding.

ASTM A234 WP92 EN 1.4901 EN 10253 Type B TUV · PED

P92 Buttweld Pipe Fittings

Grade 92 / EN 1.4901 (X10CrWMoVNb9-2) — 9Cr-2W-Mo advanced creep-strength steel for ultra-supercritical (USC) and advanced ultra-supercritical (AUSC) power generation. Delivers ~15% higher allowable stress than P91 at 600°C+. ASME B16.9 and EN 10253-3 Type B. EN 10204 3.1 standard; 3.2 TPI on request.

½″–48″

Size Range

650°C

Max Service Temp

620 MPa

Min Tensile (EN)

EN 10204

3.1 Std / 3.2 On Req.

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P92 Grade Equivalents

ASTM	EN W.Nr.	EN Name	Japanese (JIS)	UNS	ASME P-No.
A234 WP92	1.4901	X10CrWMoVNb9-2	STPA E12 (approx.)	K92460	15E, Gr 1
A182 F92 (forged)	1.4901	X10CrWMoVNb9-2	—	—	15E
A335 P92 (pipe)	1.4901	X10CrWMoVNb9-2	—	—	15E

Chemical Composition — P92 / 1.4901

Standard	C	Cr	Mo	W	V	Nb	B	N
ASTM A234 WP92	0.07–0.13	8.50–9.50	0.30–0.60	1.50–2.00	0.15–0.25	0.04–0.09	0.001–0.006	0.03–0.07
EN 1.4901 (EN 10253-3)	0.07–0.13	8.50–9.50	0.30–0.60	1.50–2.00	0.15–0.25	0.04–0.09	0.001–0.006	0.03–0.07

W (tungsten) and B (boron) additions distinguish P92 from P91. Mo is significantly lower in P92 — verify chemistry certificates carefully; P91 and P92 look similar but are NOT interchangeable.

Mechanical Properties — P92 / 1.4901

Standard	Min. UTS (MPa)	Min. YS (MPa)	Elongation (%)	Max. Hardness	HT Condition
ASTM A234 WP92	620	440	≥20%	265 HBW	N+T
EN 1.4901 (EN 10253-3)	620–850	≥440	≥19%	265 HBW	N+T

P91 vs P92 — Key Differences

Property	P91 / 1.4903	P92 / 1.4901
Mo content	0.85–1.05%	0.30–0.60%
W (tungsten)	None	1.50–2.00%
B (boron)	None	0.001–0.006%
PWHT temperature	745–775°C	750–780°C
Welding filler	ER90S-B9	ER90S-B9M (W-bearing)
Allowable stress at 600°C	~114 MPa	~133 MPa (~+17%)
Primary application	Supercritical power	Ultra-supercritical power

Critical Welding & PWHT Requirements

⚠ Use ER90S-B9M (W-bearing) Filler — Not Standard B9

P92 requires the W-bearing filler ER90S-B9M for GTAW and E9015-B9 for SMAW. Using standard ER90S-B9 (intended for P91) on P92 joints will produce a weld deposit with insufficient W content, degrading elevated-temperature creep strength. Verify filler certifications explicitly state the W content.

Preheat Temperature

200–250°C minimum. Do not allow the joint to cool below 200°C during welding.

Inter-pass Temperature

Maximum 300°C.

Filler Metal

ER90S-B9M (GTAW/TIG, W-bearing) or E9015-B9 (SMAW). Confirm W% on filler certificate.

PWHT Temperature

750–780°C. Hold minimum 1 hour per 25mm wall, minimum 2 hours for heavy wall.

Cooling

Furnace cool to 300°C, then air cool. Chart-recorded PWHT cycles required.

Post-PWHT Hardness

Weld and HAZ hardness ≤265 HBW after PWHT. Hardness survey report required.

EN 1.4901 Fittings (European) P91 Pipe Fittings P22 Pipe Fittings EN 10253 Type B Guide Quality & EN 10204

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