Material family47 grade data sheets

Chrome-moly alloy steel grades — F5, F9, F11, F22, F91

Chrome-moly steels are low-alloy steels with 1–9 % chromium and 0.5–1 % molybdenum. Chromium gives oxidation and sulphidation resistance; molybdenum gives creep strength at high temperature. They are the standard choice for steam and hot hydrocarbon service above the carbon-steel range.

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What chrome-moly alloy steel is

Grades are named after their alloy content: F11 / P11 is 1¼Cr-½Mo, F22 / P22 is 2¼Cr-1Mo, F5 / P5 is 5Cr-½Mo, F9 / P9 is 9Cr-1Mo, and F91 / P91 is 9Cr-1Mo modified with vanadium and niobium for much higher creep strength.

Chromium 1–9.5 % and molybdenum 0.44–1.13 %
F91 / P91 / WP91 add vanadium, niobium and nitrogen
Supplied normalised and tempered, or annealed
Hardness ranges controlled for weldability and hydrogen service

Key properties

Typical service range	425–600 °C (F91 to about 650 °C)
F11 Cl.2 / F22 Cl.3 yield, min	275 / 310 MPa
F91 yield, min	415 MPa
ASME B16.5 material groups	1.9 (F11), 1.10 (F22), 1.13 (F5), 1.14 (F9), 1.15 (F91)

Chrome-moly alloy steel grades compared

Chemistry and minimum room-temperature properties from the governing ASTM / ASME / API specifications. Open any grade for its full data sheet and PDF.

Grade	Form	UNS	Cr%	Ni%	Mo%	C%	YieldMPa min	TensileMPa min
ASTM A182 F11 Cl.2	Forged flanges & fittings	K11572	1.00–1.50	—	0.44–0.65	0.10–0.20	275	485
ASTM A182 F22 Cl.3	Forged flanges & fittings	K21590	2.00–2.50	—	0.87–1.13	0.05–0.15	310	515
ASTM A182 F91	Forged flanges & fittings	K90901	8.0–9.5	0.40 max	0.85–1.05	0.08–0.12	415	620
ASTM A234 WP11 Cl.1	Wrought butt-weld fittings	K11597	1.00–1.50	—	0.44–0.65	0.05–0.15	205	415
ASTM A234 WP22 Cl.1	Wrought butt-weld fittings	K21590	1.90–2.60	—	0.87–1.13	0.05–0.15	205	415
ASTM A335 P11	Seamless pipe	K11597	1.00–1.50	—	0.44–0.65	0.05–0.15	205	415
ASTM A335 P22	Seamless pipe	K21590	1.90–2.60	—	0.87–1.13	0.05–0.15	205	415
ASTM A335 P91	Seamless pipe	K90901	8.00–9.50	0.40 max	0.85–1.05	0.08–0.12	415	585
ASTM A182 F5	Forged flanges & fittings	K41545	4.0–6.0	0.50 max	0.44–0.65	0.15 max	275	485
ASTM A182 F9	Forged flanges & fittings	K90941	8.0–10.0	—	0.90–1.10	0.15 max	380	585
ASTM A182 F12 Cl.2	Forged flanges & fittings	K11564	0.80–1.25	—	0.44–0.65	0.10–0.20	275	485
ASTM A234 WP5 Cl.1	Wrought butt-weld fittings	K41545	4.0–6.0	—	0.44–0.65	0.15 max	205	415
ASTM A234 WP9 Cl.1	Wrought butt-weld fittings	K90941	8.0–10.0	—	0.90–1.10	0.15 max	205	415
ASTM A234 WP91 Type 1	Wrought butt-weld fittings	K90901	8.0–9.5	0.40 max	0.85–1.05	0.08–0.12	415	585
ASTM A335 P5	Seamless pipe	K41545	4.00–6.00	—	0.45–0.65	0.15 max	205	415
ASTM A335 P9	Seamless pipe	K90941	8.00–10.00	—	0.90–1.10	0.15 max	205	415
ASTM A335 P12	Seamless pipe	K11562	0.80–1.25	—	0.44–0.65	0.05–0.15	220	415
ASTM A217 WC6	Alloy steel castings	J12072	1.00–1.50	—	0.45–0.65	0.05–0.20	275	485
ASTM A217 WC9	Alloy steel castings	J21890	2.00–2.75	—	0.90–1.20	0.05–0.18	275	485
ASTM A182 F1	Forged flanges & fittings	K12822	—	—	0.44–0.65	0.28 max	275	485
ASTM A182 F2	Forged flanges & fittings	K12122	0.50–0.81	—	0.44–0.65	0.05–0.21	275	485
ASTM A182 F5a	Forged flanges & fittings	K42544	4.0–6.0	0.50 max	0.44–0.65	0.25 max	450	620
ASTM A182 F11 Cl.1	Forged flanges & fittings	K11597	1.00–1.50	—	0.44–0.65	0.05–0.15	205	415
ASTM A182 F11 Cl.3	Forged flanges & fittings	K11572	1.00–1.50	—	0.44–0.65	0.10–0.20	310	515
ASTM A182 F12 Cl.1	Forged flanges & fittings	K11562	0.80–1.25	—	0.44–0.65	0.05–0.15	220	415
ASTM A182 F21	Forged flanges & fittings	K31545	2.7–3.3	—	0.80–1.06	0.05–0.15	310	515
ASTM A182 F22 Cl.1	Forged flanges & fittings	K21590	2.00–2.50	—	0.87–1.13	0.05–0.15	205	415
ASTM A182 F92	Forged flanges & fittings	K92460	8.50–9.50	0.40 max	0.30–0.60	0.07–0.13	440	620
ASTM A335 P1	Seamless pipe	K11522	—	—	0.44–0.65	0.10–0.20	205	380
ASTM A335 P2	Seamless pipe	K11547	0.50–0.81	—	0.44–0.65	0.10–0.20	205	380
ASTM A335 P15	Seamless pipe	K11578	—	—	0.44–0.65	0.05–0.15	205	415
ASTM A335 P21	Seamless pipe	K31545	2.65–3.35	—	0.80–1.06	0.05–0.15	205	415
ASTM A335 P23	Seamless pipe	UNS K41650	1.90–2.60	0.40 max	0.05–0.30	0.04–0.10	400	510
ASTM A335 P92	Seamless pipe	K92460	8.50–9.50	0.40 max	0.30–0.60	0.07–0.13	440	620
ASTM A234 WP1	Wrought butt-weld fittings	K12821	—	—	0.44–0.65	0.28 max	205	380
ASTM A234 WP11 Cl.2	Wrought butt-weld fittings	K11572	1.00–1.50	—	0.44–0.65	0.05–0.20	275	485
ASTM A234 WP11 Cl.3	Wrought butt-weld fittings	K11572	1.00–1.50	—	0.44–0.65	0.05–0.20	310	520
ASTM A234 WP12 Cl.1	Wrought butt-weld fittings	K12062	0.80–1.25	—	0.44–0.65	0.05–0.20	220	415
ASTM A234 WP22 Cl.3	Wrought butt-weld fittings	K21590	1.90–2.60	—	0.87–1.13	0.05–0.15	310	520
ASTM A234 WP92	Wrought butt-weld fittings	K92460	8.50–9.50	0.40 max	0.30–0.60	0.07–0.13	440	620
ASTM A217 WC1	Alloy steel castings	J12524	—	—	0.45–0.65	0.25 max	240	450
ASTM A217 C5	Alloy steel castings	J42045	4.00–6.50	—	0.45–0.65	0.20 max	415	620
ASTM A217 C12	Alloy steel castings	J82090	8.00–10.00	—	0.90–1.20	0.20 max	415	620
ASTM A217 C12A	Alloy steel castings	J84090	8.0–9.5	0.40 max	0.85–1.05	0.08–0.12	415	585
ASTM A387 Grade 11 Cl.2	Pressure-vessel plate	K11789	1.00–1.50	—	0.45–0.65	0.05–0.17	310	515
ASTM A387 Grade 22 Cl.2	Pressure-vessel plate	K21590	2.00–2.50	—	0.90–1.10	0.05–0.15	310	515
ASTM A387 Grade 91 Cl.2	Pressure-vessel plate	K90901	8.00–9.50	0.40 max	0.85–1.05	0.08–0.12	415	585

Reference information compiled from the published standard for convenience. It does not replace the current edition of the governing standard, which takes precedence. Verify critical dimensions and properties before design, purchase or fabrication. Teshi Engineers & Sales Promoters (P) Ltd accepts no liability for errors or omissions.

Specifications by product form

Product form	Grades
Forged flanges & fittings	ASTM A182 F11 Cl.2, ASTM A182 F22 Cl.3, ASTM A182 F91, ASTM A182 F5, ASTM A182 F9, ASTM A182 F12 Cl.2, ASTM A182 F1, ASTM A182 F2, ASTM A182 F5a, ASTM A182 F11 Cl.1, ASTM A182 F11 Cl.3, ASTM A182 F12 Cl.1, ASTM A182 F21, ASTM A182 F22 Cl.1, ASTM A182 F92
Wrought butt-weld fittings	ASTM A234 WP11 Cl.1, ASTM A234 WP22 Cl.1, ASTM A234 WP5 Cl.1, ASTM A234 WP9 Cl.1, ASTM A234 WP91 Type 1, ASTM A234 WP1, ASTM A234 WP11 Cl.2, ASTM A234 WP11 Cl.3, ASTM A234 WP12 Cl.1, ASTM A234 WP22 Cl.3, ASTM A234 WP92
Seamless pipe	ASTM A335 P11, ASTM A335 P22, ASTM A335 P91, ASTM A335 P5, ASTM A335 P9, ASTM A335 P12, ASTM A335 P1, ASTM A335 P2, ASTM A335 P15, ASTM A335 P21, ASTM A335 P23, ASTM A335 P92
Alloy steel castings	ASTM A217 WC6, ASTM A217 WC9, ASTM A217 WC1, ASTM A217 C5, ASTM A217 C12, ASTM A217 C12A
Pressure-vessel plate	ASTM A387 Grade 11 Cl.2, ASTM A387 Grade 22 Cl.2, ASTM A387 Grade 91 Cl.2

Where chrome-moly alloy steel is used

Main steam, hot and cold reheat lines in power plants
Refinery heaters, hydrocrackers and reformers
Hydrogen and high-temperature sulphidic service
Boiler headers and superheaters

Welding and fabrication

Cr-Mo steels need preheat, controlled interpass temperature and post-weld heat treatment. P91/F91 is particularly sensitive: tempering temperature and time must be controlled tightly, and hardness is checked after PWHT. Positive material identification (PMI) is standard on every piece.

FAQ

Chrome-moly alloy steel: common questions

What is the difference between F11 and F22?

F11 is 1¼Cr-½Mo; F22 is 2¼Cr-1Mo. F22 has more chromium and molybdenum, so it has higher creep strength and better resistance to hydrogen and high-temperature corrosion.

Why is F91 used in power plants?

F91 (9Cr-1Mo-V) has roughly twice the creep strength of F22 at 550–600 °C, so walls can be thinner and lighter for the same pressure — important for main steam lines in supercritical units.

Which grades match P91 pipe?

A234 WP91 butt-weld fittings, A182 F91 flanges and forged fittings, and A217 C12A valve castings.