What are the classes of ASTM A182 F22 and which is most common?

ASTM A182 F22 is available in two heat treatment classes: Class 1 (annealed) with UTS ≥ 415 MPa / YS ≥ 205 MPa, and Class 3 (normalized and tempered, N&T) with UTS ≥ 515 MPa / YS ≥ 310 MPa. Class 3 (N&T) is by far the most commonly specified for flanges and pressure-containing components in hydroprocessing service, as its higher strength results in better pressure ratings at elevated temperature. Class 1 is used for lower-stress applications or when enhanced toughness at lower temperatures is needed.

What is the composition of ASTM A182 F22?

ASTM A182 F22 contains: Chromium 1.90–2.60%, Molybdenum 0.87–1.13%, Carbon 0.05–0.15%, Manganese 0.30–0.60%, Silicon ≤ 0.50%, Phosphorus ≤ 0.025%, Sulfur ≤ 0.025%. The 2.25Cr-1Mo nominal composition (midpoints: 2.25% Cr, 1.0% Mo) is a carefully balanced alloy providing excellent creep strength, good high-temperature hydrogen attack resistance per API 941, and satisfactory oxidation resistance up to 649°C.

What is the maximum service temperature for ASTM A182 F22 Class 3 flanges?

ASTM A182 F22 Class 3 flanges are rated for continuous service up to 649°C (1200°F) per ASME B16.5 Material Group 3.3 pressure-temperature tables. Class 3 (N&T) provides significantly higher pressure ratings than Class 1 at elevated temperatures. At 649°C, Class 150 F22 Class 3 allows approximately 105–115 psi, vs near-zero for carbon steel A105 which falls off rapidly above 538°C.

What filler metal is used for welding ASTM A182 F22 flanges?

The standard filler metals for ASTM A182 F22 are ER90S-B3 (GTAW/GMAW) and E9018-B3 (SMAW) per AWS A5.28 and A5.5 respectively — these are 2.25Cr-1Mo matching consumables. For less critical service or when matching the lower Class 1 strength, ER80S-B3 / E8018-B3 may be used. Minimum preheat is 175°C (200°C for heavy sections), interpass temperature 175–320°C, and PWHT at 675–760°C is mandatory for all pressure-containing welds regardless of thickness.

Is PWHT mandatory for ASTM A182 F22 flanges?

Yes. PWHT at 675–760°C is mandatory for all pressure-containing welds on F22 flanges regardless of wall thickness. The 2.25Cr-1Mo composition has significant hardenability — as-welded HAZ hardness routinely exceeds 300 HV (well above the NACE MR0175 limit of 250 HBW). PWHT tempers the martensitic HAZ, restores toughness, relieves residual stress, and ensures hardness compliance for sour service. Additionally, temper embrittlement considerations for F22 in hydroprocessing require careful control of PWHT cooling rates through 375–575°C.

What is the DIN or European equivalent of ASTM A182 F22?

The primary European equivalent of ASTM A182 F22 is DIN 1.7380, designated 10CrMo9-10 per EN 10216-2 (seamless steel tubes) and EN 10222-2 (steel forgings). The companion European pipe grade is P265GH (lower temperature) or 10CrMo9-10. The DIN designation 1.7383 (12CrMo9-10) is also sometimes cited as a close equivalent. For flanges specifically, EN 1092-1 flanges in material grade 10CrMo9-10 correspond to ASME B16.5 F22 flanges.

What is temper embrittlement in F22 and how is it controlled?

Temper embrittlement is a loss of impact toughness in F22 caused by slow cooling through 375–575°C, which segregates trace impurities (P, Sn, Sb, As) to grain boundaries. This raises the ductile-to-brittle transition temperature (DBTT), increasing brittle fracture risk during cold pressurisation. For hydrocracking service, API 934-A requires the J-factor (J = (Mn + Si) × (P + Sn) × 10⁴) ≤ 100 and Bruscato X-factor (X = (10P + 5Sb + 4Sn + As)/100) ≤ 15 ppm. A step-cool test per API 934-A is mandatory for F22 in critical hydroprocessing service to verify embrittlement resistance.

What pipe, fitting and casting grades correspond to ASTM A182 F22?

The companion grades for ASTM A182 F22 are: ASTM A335 Grade P22 (seamless ferritic alloy steel pipe, 2.25Cr-1Mo), ASTM A234 Grade WP22 (wrought alloy steel pipe fittings), and ASTM A217 Grade WC9 (alloy steel castings, 2.25Cr-1Mo — for valve bodies and other cast components). Using these companion grades maintains metallurgical consistency and simplifies WPS qualification throughout a hydroprocessing piping system.

What is the API 941 Nelson curve limit for F22 in hydrogen service?

Per API 941, ASTM A182 F22 (2.25Cr-1Mo) plots on the '2.25Cr-1Mo' Nelson curve. At a hydrogen partial pressure of 70 bar, the safe operating temperature limit is approximately 340°C. At lower H₂ partial pressures, the safe limit is higher — for example at 35 bar H₂ the limit rises to approximately 380°C. If the operating point plots above the F22 Nelson curve, upgrade to F21 (3Cr-1Mo) or F5/F9 must be considered. Always verify against the current API 941 edition for the specific operating conditions.

ASTM A182 F22 Alloy Steel Flanges Manufacturer in India

What is ASTM A182 F22 Alloy Steel?

ASTM A182 F22 (ASME SA182 F22) is a 2.25% chromium – 1% molybdenum (2.25Cr-1Mo) low-alloy ferritic steel covered under ASTM A182 — the primary specification for forged alloy-steel pipe flanges, fittings, and valve bodies for high-temperature and hydrogen service. Designated UNS K21590 and equivalent to DIN 1.7380 (10CrMo9-10) in European standards, F22 is the most widely used Cr-Mo grade in petroleum refinery hydroprocessing — the undisputed workhorse of hydrocracker and hydrotreater piping systems worldwide.

The 2.25% chromium provides robust resistance to high-temperature hydrogen attack (HTHA) per the API 941 Nelson curves, while the 1% molybdenum — double the Mo content of F11 (0.5%) — delivers strong creep-rupture properties up to 649°C and stabilises carbides against hydrogen embrittlement. F22 Class 3 (normalized and tempered, N&T) achieves a minimum UTS of 515 MPa and YS of 310 MPa — significantly higher than F22 Class 1 (annealed) and F5/F9, making it one of the strongest standard Cr-Mo flanges at both ambient and elevated temperatures.

Tesco Steel & Engineering manufactures and exports F22 flanges in all types — WNRF, SORF, BLRF, SWRF, LJTF, THRF — from NPS ½ to 60, Class 150 to 2500, per ASME B16.5 and B16.47, with full EN 10204 3.1/3.2 material certification and optional temper embrittlement testing per API 934-A.

F22 in the Chromium-Molybdenum Alloy Steel Family

F22's 2.25Cr-1Mo composition is the established industry standard for the most demanding refinery service conditions before stepping up to the more complex F91 (modified 9Cr-1Mo-V). It bridges the gap between F11 (moderate H₂ resistance) and the 5–9Cr grades (extreme sulfidation service):

F11

1.25Cr-0.5Mo

H₂ service — mild
Max 593°C
UTS 485 MPa (Cl.2)
Group 3.1
Moderate H₂ partial pressure

F22 ★

2.25Cr-1Mo Cl.3

Hydroprocessing standard
Max 649°C
UTS 515 MPa (Cl.3)
Group 3.3
Hydrocracker / hydrotreater

● Industry Standard ●

F91

9Cr-1Mo-V-Nb

Ultra-high creep strength
Max 650°C+
UTS 585 MPa
Higher creep strength
Creep-limited design

Why F22 Class 3 is the hydroprocessing default: (1) The 2.25Cr-1Mo composition places it safely within the API 941 Nelson curve for typical hydroprocessing temperatures up to ~340°C at high H₂ partial pressure. (2) Class 3 N&T (515 MPa UTS) delivers 3.3 Group P-T ratings significantly better than F11 above 400°C. (3) The complete companion system — A335 P22 pipe, A234 WP22 fittings, A217 WC9 castings — is fully developed and universally available. (4) F22 WPS qualification databases are extensive and well-established at all major fabricators.

ASTM A182 F22 Chemical Composition

The following composition requirements apply per ASTM A182 / ASME SA182 for Grade F22 (both Class 1 and Class 3 have the same composition requirements; the difference is heat treatment):

Element	Min %	Max %	Significance
Carbon (C)	0.05	0.15	Minimum 0.05% (unlike F11/F5/F9) to ensure adequate strength; max 0.15% for weldability
Manganese (Mn)	0.30	0.60	Controlled low — higher Mn increases J-factor (temper embrittlement susceptibility)
Silicon (Si)	—	0.50	Deoxidation; contributes to J-factor — should be minimised for critical H₂ service
Phosphorus (P)	—	0.025	Critical temper embrittlement element — specify ≤ 0.010% for hydroprocessing service
Sulfur (S)	—	0.025	Low for toughness and clean forging microstructure
Chromium (Cr)	1.90	2.60	H₂ attack resistance (Nelson curves), oxidation resistance, moderate sulfidation resistance
Molybdenum (Mo)	0.87	1.13	Primary creep resistance element; carbide stability against HTHA; 2× F11's 0.44–0.65%

Temper Embrittlement Chemistry Control: For hydroprocessing service, procure F22 heats with P ≤ 0.010%, Sn ≤ 0.010%, Sb ≤ 0.003%, As ≤ 0.010%, and verify J-factor = (Mn + Si) × (P + Sn) × 10⁴ ≤ 100 and Bruscato X = (10P + 5Sb + 4Sn + As)/100 ≤ 15 ppm. These requirements are mandatory per API 934-A for hydrocracking service.

Mechanical Properties — F22 Classes vs Other Cr-Mo Grades

F22 is the only standard Cr-Mo grade in A182 that comes in two significantly different heat treatment conditions that are both widely used in the field:

Property	F22 Class 3 (N&T)	F22 Class 1 (Ann.)	F11 Cl.2 (N&T)	F5 (N&T)	F9 (N&T)
UTS (min)	515 MPa	415 MPa	485 MPa	415 MPa	585 MPa
YS (min)	310 MPa	205 MPa	275 MPa	205 MPa	380 MPa
Elongation (min)	20%	20%	20%	20%	20%
Hardness (max)	241 HBW	241 HBW	207 HBW	241 HBW	241 HBW
Heat Treatment	N&T	Annealed	N&T	N&T	N&T
Max Service Temp	649°C	649°C	593°C	649°C	649°C
ASME B16.5 Group	3.3	3.2	3.1	5.1	5.2
H₂ Nelson Curve	2.25Cr line	2.25Cr line	1.25Cr line	5Cr line	9Cr line

F22 Class 3 has the highest UTS of the 2.25Cr-1Mo family variants. For most hydroprocessing applications, Class 3 is specified due to its superior P-T ratings at elevated temperature under ASME B16.5 Group 3.3.

Temper Embrittlement — The Critical F22 Design Issue

Temper embrittlement is the most important metallurgical consideration for F22 in hydroprocessing service. It is not simply a welding or PWHT issue — it is a life-cycle material integrity issue that must be addressed from material procurement through to operational startup procedures.

What is it?

Trace impurities (P, Sn, Sb, As) segregate to grain boundaries during slow cooling through 375–575°C, raising the ductile-to-brittle transition temperature (DBTT)

The Risk

Brittle fracture during cold startup / pressurisation if DBTT has risen above ambient temperature. Catastrophic failure risk in high-pressure H₂ systems

Controls

Low-impurity heats (J ≤ 100, X ≤ 15), step-cool test per API 934-A, warm-up procedures before pressurisation, controlled PWHT cooling rates

The two industry-standard metrics for predicting temper embrittlement susceptibility in F22 are:

Metric	Formula	Limit for H₂ Service	Reference
J-Factor (Watanabe)	(Mn + Si) × (P + Sn) × 10⁴ (all elements in wt%)	≤ 100	API 934-A; NACE
X-Factor (Bruscato)	(10P + 5Sb + 4Sn + As) / 100 (all elements in ppm)	≤ 15 ppm	API 934-A; ASME

A step-cool test per API 934-A (slow thermal cycle through the embrittlement range followed by Charpy V-notch testing before and after) provides direct experimental verification of embrittlement susceptibility and is mandatory for F22 in critical hydroprocessing service.

API 941 Nelson Curves — F22 in Hydrogen Service

API 941 (Steels for Hydrogen Service at Elevated Temperatures and Pressures in Petroleum Refineries) provides safe-operating-limit curves for Cr-Mo steels in hydrogen environments. F22 (2.25Cr-1Mo) plots on the 2.25Cr-1Mo curve — significantly above F11 (1.25Cr) and suitable for the majority of hydroprocessing reactor and separator service conditions:

Material	Safe Temp @ 35 bar H₂	Safe Temp @ 70 bar H₂	Safe Temp @ 140 bar H₂
Carbon Steel (A105)	~250°C	~220°C	~190°C
F11 (1.25Cr-0.5Mo)	~330°C	~295°C	~260°C
F22 (2.25Cr-1Mo) ★	~380°C	~340°C	~310°C
F21 (3Cr-1Mo)	~410°C	~370°C	~330°C
F5 (5Cr-0.5Mo)	~450°C	~410°C	~365°C
F9 (9Cr-1Mo)	~500°C	~450°C	~400°C

Values are approximate and indicative. Always verify against the current edition of API 941 for actual design decisions. Safe temperatures increase at lower H₂ partial pressures.

For most commercial hydrocracking units operating at 300–380°C with H₂ partial pressures of 60–140 bar, F22 provides a comfortable margin above the F22 Nelson curve boundary. Hydrocracker reactor walls — which see much higher temperatures (420–450°C) — require a separate material assessment and are typically designed as thick-walled vessels, not flanges.

Grade Cross-Reference — ASTM A182 F22 International Equivalents

Standard	Designation	Notes
ASTM / ASME (Flanges)	A182 / SA182 Grade F22	Class 1 (annealed) or Class 3 (N&T) — specify class explicitly
UNS	K21590	Unified Numbering System
ASTM (Pipe)	A335 Grade P22	Seamless ferritic alloy steel pipe — 2.25Cr-1Mo
ASTM (Fittings)	A234 Grade WP22	Wrought alloy steel pipe fittings — 2.25Cr-1Mo
ASTM (Castings)	A217 Grade WC9	Alloy steel castings — 2.25Cr-1Mo (valve bodies, etc.)
DIN / EN (Forgings)	1.7380 / 10CrMo9-10	EN 10222-2 — closest European forging equivalent
EN (Pipe)	EN 10216-2 / 10CrMo9-10	European seamless pressure pipe grade
DIN (alt.)	1.7383 / 12CrMo9-10	Slightly higher C; sometimes used as equivalent
ASME B16.5 Group (Cl.3)	Group 3.3	Highest-rated standard Cr-Mo group in B16.5 below Group 5
ASME B16.5 Group (Cl.1)	Group 3.2	Lower P-T ratings than Class 3
Weld Filler — GTAW (Cl.3)	ER90S-B3	AWS A5.28 — 2.25Cr-1Mo, higher strength matching
Weld Filler — SMAW (Cl.3)	E9018-B3	AWS A5.5 — low-hydrogen, 2.25Cr-1Mo
Weld Filler — GTAW (Cl.1)	ER80S-B3	AWS A5.28 — lower strength, suitable for Class 1
Weld Filler — SMAW (Cl.1)	E8018-B3	AWS A5.5 — lower strength matching

ASTM A182 F22 Flange Dimensions — ASME B16.5 Class 150 WNRF

Dimensions are per ASME B16.5, independent of material. Full tables for all classes (150–2500) and face types are available on our Flange Dimensions page.

NPS	OD (mm)	BC (mm)	Bolts (no.)	Bolt ⌀ (mm)	Flange Thick. (mm)	Approx. Wt. (kg)
½"	88.9	60.3	4	15.7	9.7	0.4
¾"	98.4	69.8	4	15.7	11.2	0.6
1"	107.9	79.4	4	15.7	12.7	0.8
1½"	127.0	98.4	4	15.7	14.3	1.3
2"	152.4	120.6	4	19.0	15.9	2.2
3"	190.5	152.4	4	19.0	19.0	4.0
4"	228.6	190.5	8	19.0	22.4	7.0
6"	279.4	241.3	8	22.2	25.4	13.0
8"	342.9	298.4	8	22.2	28.6	21.0
10"	406.4	362.0	12	25.4	31.8	36.0
12"	482.6	431.8	12	25.4	35.0	54.0
14"	533.4	476.2	12	28.6	38.1	75.0
16"	596.9	539.7	16	28.6	41.4	105.0
18"	635.0	577.8	16	31.7	44.4	135.0
20"	698.5	635.0	20	31.7	47.6	165.0
24"	812.8	749.3	20	35.0	50.8	270.0

NPS 26–60 available per ASME B16.47 Series A & B. Custom bores, special schedules, NACE-compliant and step-cool-tested heats on request. Request dimensional drawings.

Welding Guidelines for ASTM A182 F22 Flanges

⚠ PWHT is MANDATORY for ALL pressure-containing welds on F22 — no thickness exemption. The 2.25Cr-1Mo composition hardenability is significantly greater than carbon steel — as-welded HAZ hardness commonly exceeds 300–350 HV, far above NACE MR0175's 250 HBW limit. PWHT at 675–760°C with controlled cooling through the 575–375°C embrittlement zone is essential for both hardness compliance and temper embrittlement prevention.

Parameter	Class 3 (N&T) — Standard Hydroprocessing
Filler — GTAW	ER90S-B3 (AWS A5.28) — 2.25Cr-1Mo matching strength
Filler — SMAW	E9018-B3 (AWS A5.5) — low-hydrogen; bake 300–350°C min 1 hr before use
Filler — FCAW	E91T1-B3 (AWS A5.29) — suitable for flat/horizontal position
Minimum Preheat	175°C (350°F); 200°C (390°F) for t > 25 mm or high restraint
Interpass Temperature	175–320°C — maintain throughout; do not allow joint to cool to ambient mid-pass
PWHT Temperature	675–760°C (1250–1400°F)
PWHT Hold Time	1 hour per 25 mm wall thickness; minimum 1 hour total
PWHT Heating Rate	≤ 150°C/hour above 400°C
PWHT Cooling Rate	≤ 55°C/hour to 300°C (controlled slow cool to minimise embrittlement risk) — then air cool
Hardness after PWHT	≤ 22 HRC (≤ 250 HBW) per NACE MR0175 for sour / H₂S service
Temper Embrittlement	Verify J-factor ≤ 100 and X-factor ≤ 15 ppm on base metal and weld metal MTRs
Step-cool test	Per API 934-A — mandatory for critical hydroprocessing service

Applications of ASTM A182 F22 Flanges

F22 (2.25Cr-1Mo) is the default material for high-pressure, high-temperature hydrogen service in petroleum refining and power generation. Its applications span the full range of hydroprocessing units:

Hydrocracker (HCC) Units: Reactor feed/effluent flanges, high-pressure separator nozzles, recycle gas compressor suction/discharge
Hydrotreater (HDT) Units: Naphtha, kerosene, diesel and vacuum gas oil hydrotreating circuits at elevated H₂ partial pressure
Atmospheric Residue Desulfurization (ARDS): High-pressure reactor and separator flanges in resid treating units
Vacuum Residue Desulfurization (VRDS): Heavy feed reactor circuits at high temperature and pressure
Hot High-Pressure Separators: HHPS nozzle and piping flanges in hydroprocessing complexes

H₂ Make-Up Compressor Piping: High-pressure hydrogen supply headers and block valves
Catalytic Reformers: High-pressure separator and recycle compressor flanges with H₂-rich streams
Power Plant Steam Headers: Main steam piping flanges above 500°C where F11 creep strength is insufficient
Heat Recovery Steam Generators (HRSG): High-temperature superheater outlet flanges
Boiler Drum Nozzles: High-pressure steam drum connections in coal-fired and combined-cycle power plants

Applicable Standards for ASTM A182 F22 Flanges

Standard	Scope
ASTM A182 / ASME SA182	Primary material specification for F22 forged flanges — specify Class 1 or Class 3
ASME B16.5	Pipe flanges and flanged fittings, NPS ½–24, Class 150–2500
ASME B16.47	Large diameter steel flanges, NPS 26–60, Series A & B
ASME B16.20	Metallic gaskets including RTJ ring gaskets — mandatory for Class 900+ H₂ service
ASME B16.25	Butt-welding ends for weld neck flanges
ASME Section IX	Welding qualification — WPS/PQR for F22 (2.25Cr-1Mo base metal)
ASME B31.3	Process piping — P-T ratings, PWHT requirements for F22
API 941	Nelson curves — primary authority for F22 H₂ service design
API 934-A	Materials and fabrication for 2.25Cr-1Mo and 3Cr-1Mo equipment — step-cool test, J/X factor requirements
NACE MR0175 / ISO 15156	Hardness limits (≤ 22 HRC) for sour H₂S service after PWHT
ASTM A335 P22	Companion seamless pipe grade — 2.25Cr-1Mo
ASTM A234 WP22	Companion wrought fittings — 2.25Cr-1Mo
ASTM A217 WC9	Companion casting grade — 2.25Cr-1Mo (valve bodies)
EN 10222-2 / 10CrMo9-10	European forging equivalent (DIN 1.7380)
EN 10204 3.1 / 3.2	Mill test report certification — 3.2 recommended for hydroprocessing

ASTM A182 F22 Flange Product Range

Parameter	Range / Options
Size	NPS ½" to NPS 60" (½–24 per B16.5; 26–60 per B16.47)
Pressure Class	150, 300, 600, 900, 1500, 2500 (ASME B16.5); PN 6–PN 400 (EN 1092-1)
Heat Treatment Class	Class 1 (Annealed) or Class 3 (Normalized & Tempered) — specify; Class 3 default for flanges
Flange Types	WN, SO, BL, SW, TR, LJ, LWN, Reducing, Spectacle Blind, Paddle Blind
Face Types	Raised Face (RF), Ring Type Joint (RTJ), Flat Face (FF), LT/G, ST/G, LM/F
Schedule / Wall	Sch 40, 80, 120, 160, XS, XXS; custom bore available
Testing	Hydrostatic test, PMI, hardness survey post-PWHT, UT, RT, MPT, Charpy impact, step-cool test per API 934-A
Chemistry Controls	Standard ASTM A182; or enhanced: P ≤ 0.010%, Sn ≤ 0.010%, J ≤ 100, X ≤ 15 ppm for hydroprocessing
Documentation	EN 10204 3.1 standard; 3.2 for critical service; API 934-A step-cool test reports; NACE/PED/ATEX certificates

For a quote with step-cool test certification or enhanced J/X factor chemistry, please submit an inquiry or WhatsApp +91-9223366922.

Frequently Asked Questions — ASTM A182 F22 Flanges

Questions sourced from AI search platforms, engineering procurement teams, and refinery materials-engineering practice.

Q1: What is ASTM A182 F22 and why is it the standard for hydrocracking?

ASTM A182 F22 is the 2.25Cr-1Mo alloy steel forging specification (UNS K21590, DIN 1.7380 / 10CrMo9-10) that has become the default material for hydrocracker and hydrotreater piping flanges worldwide. Its 2.25% Cr provides adequate placement on the API 941 Nelson curve for H₂ service up to ~340°C at 70 bar H₂ partial pressure, while the 1% Mo delivers superior creep resistance over F11 (0.5% Mo) and the same resistance as F21. Class 3 (N&T) achieves 515 MPa UTS — the highest of the 2.25Cr family — combined with a fully developed companion material system (A335 P22 pipe, A234 WP22 fittings, A217 WC9 castings) and established WPS databases at fabricators globally.

Q2: What is the difference between F22 Class 1 and Class 3?

Both classes have identical composition (Cr 1.90–2.60%, Mo 0.87–1.13%) — the difference is exclusively in heat treatment and resulting mechanical properties. Class 1 (annealed): UTS ≥ 415 MPa, YS ≥ 205 MPa, ASME B16.5 Group 3.2 — lower strength, lower P-T ratings. Class 3 (normalized & tempered): UTS ≥ 515 MPa, YS ≥ 310 MPa, ASME B16.5 Group 3.3 — the standard for hydroprocessing flanges. Class 3 is almost universally specified for pressure-retaining components. Class 1 is occasionally used for large-bore low-stress flanges or when superior toughness at low temperature is needed. Always specify the class explicitly in the purchase specification.

Q3: Is PWHT mandatory for F22 flanges regardless of wall thickness?

Yes — PWHT at 675–760°C is mandatory for all pressure-containing welds on F22, with no wall thickness exemption. The 2.25Cr-1Mo composition has significantly greater hardenability than carbon steel. As-welded HAZ hardness regularly exceeds 300–350 HV (well above the NACE MR0175 limit of 250 HBW). Beyond hardness, the specific cooling rate during PWHT is critical: slow cooling through 575–375°C prevents temper embrittlement, while rapid cooling through this same range (even after correct PWHT temperature) can accelerate embrittlement susceptibility. Time-temperature PWHT records must be retained.

Q4: What is the DIN / European equivalent of ASTM A182 F22?

The primary European equivalent is DIN 1.7380, designated 10CrMo9-10 per EN 10216-2 (seamless tubes) and EN 10222-2 (steel forgings). For flanges specifically, EN 1092-1 flanges in material 10CrMo9-10 correspond to ASME B16.5 F22 flanges. The designation "1.7383 / 12CrMo9-10" has slightly higher carbon and is sometimes cited as an alternative. Note that EN and ASTM composition limits are not identical — always verify heat chemistry against both standards if dual certification is required. Japanese equivalent is SFVA F22 under JIS B 2220.

Q5: What are the J-factor and X-factor requirements for F22 in hydroprocessing?

Per API 934-A, F22 used in critical hydroprocessing service must meet: J-factor = (Mn + Si) × (P + Sn) × 10⁴ ≤ 100 (all in wt%); X-factor (Bruscato) = (10P + 5Sb + 4Sn + As)/100 ≤ 15 ppm. Individual element limits typically specified: P ≤ 0.010%, Sn ≤ 0.010%, Sb ≤ 0.003%, As ≤ 0.010%. These limits are tighter than standard ASTM A182 (P ≤ 0.025%) and must be explicitly included in the purchase specification. A step-cool test per API 934-A with Charpy V-notch testing before and after step-cool treatment provides direct verification of embrittlement resistance.

Q6: What filler metal should be used for welding F22 Class 3 flanges?

For F22 Class 3 (N&T), the matching filler metals are ER90S-B3 (AWS A5.28 — for GTAW/GMAW) and E9018-B3 (AWS A5.5 — for SMAW). The "90" tensile strength designation matches Class 3's 515 MPa (75 ksi) minimum UTS level. For F22 Class 1, lower-strength ER80S-B3 / E8018-B3 may be used. All consumables must be hydrogen-controlled (low-hydrogen electrodes stored and dried at 300–350°C). Filler MTRs should also be checked for J-factor/X-factor compliance for critical hydroprocessing service welds.

Q7: What is the API 941 Nelson curve safe limit for F22 in H₂ service?

ASTM A182 F22 (2.25Cr-1Mo) plots on the 2.25Cr-1Mo Nelson curve in API 941. At 70 bar H₂ partial pressure, the safe operating temperature is approximately 340°C. At 35 bar H₂ partial pressure, the safe limit rises to approximately 380°C. If the operating point falls above the F22 line — for example, piping at 360°C with 70 bar H₂ — the material must be upgraded to F21 (3Cr-1Mo) or F5/F9. Always plot exact process conditions against the current API 941 edition, as curves have been revised over time.

Q8: What casting grade corresponds to ASTM A182 F22?

The companion casting grade for F22 is ASTM A217 Grade WC9 (2.25Cr-1Mo, normalized and tempered). WC9 is used for valve bodies, pressure vessel nozzles, and other cast components in the same hydroprocessing piping circuit as F22 flanges, A335 P22 pipe, and A234 WP22 fittings. Using all four companion grades maintains consistent 2.25Cr-1Mo metallurgy throughout the system, simplifying WPS qualification and avoiding galvanic or thermal expansion mismatches at joints.

Q9: Can ASTM A182 F22 flanges be used in sour H₂S service per NACE MR0175?

Yes. F22 is permitted for sour (H₂S) service per NACE MR0175 / ISO 15156 provided the post-PWHT hardness of the base metal, HAZ and weld does not exceed 22 HRC (250 HBW). Given the higher hardenability of 2.25Cr-1Mo, achieving this consistently requires correct PWHT (675–760°C, adequate hold time) and is verified by a full hardness survey across weld + HAZ + base metal. As-welded F22 routinely exceeds 250 HBW — PWHT is non-negotiable for sour service. EN 10204 3.2 certification with witnessed hardness testing is recommended for sour-service flanges.

Q10: Why does F22 have a higher risk of temper embrittlement than carbon steel?

The 2.25Cr-1Mo composition of F22 creates a ferritic/bainitic grain structure that is inherently more susceptible to impurity segregation at grain boundaries than plain carbon steel. The chromium and molybdenum in F22 also interact with trace impurities (particularly phosphorus and tin) to accelerate their grain boundary segregation kinetics during slow cooling through 375–575°C. In contrast, plain carbon steel grain boundary areas are less susceptible to these solute-impurity interactions. The consequence: a heat of F22 with P = 0.025% (within ASTM A182 limits but at the maximum) can develop severe temper embrittlement in service, while a heat with P = 0.008% and Sn ≤ 0.005% will remain tough throughout its service life. This is why API 934-A imposes chemistry limits beyond those in ASTM A182 for hydroprocessing F22.

'SHAPING INDUSTRIES WITH THE FINEST STEEL'