Tesco Steel & Engineering manufactures ASTM A182 F21 alloy steel flanges — the 3% chromium, 1% molybdenum (3Cr-1Mo) chrome-moly forging grade. The chromium and molybdenum give strong creep strength, elevated-temperature strength and resistance to high-temperature hydrogen attack, placing F21 between F22 (2.25Cr) and F5 (5Cr) for high-temperature, high-pressure hydrogen and hydroprocessing service. As a hardenable alloy steel it requires preheat and post-weld heat treatment. Available in weld neck, slip-on, blind, socket-weld, threaded, lap-joint, spectacle and orifice types to ASTM A182 / ASME B16.5. Class 150 to 2500, NPS 1/2″ to 24″, PN6 to PN400. ISO 9001:2015 certified. Made in India.
ASTM A182 F21 (3Cr-1Mo) Alloy Steel Flanges
A182 F21 Weld Neck & Blind Flanges
Tesco Steel & Engineering manufactures A182 F21 flanges in all types from weld neck to orifice, Class 150 to 2500 — supplied normalized-and-tempered with EN 10204 3.1 / 3.2 certification, hardness results and third-party inspection on request. Explore the wider alloy steel flange range, the neighbouring A182 F22 flanges and A182 F5 flanges, the lower-chrome A182 F11 flanges, and the flange dimension charts.
| ASTM A182 F21 flanges are available in the following specifications: | |
|---|---|
| Material Grade | ASTM A182 / A182M Grade F21 (3Cr-1Mo chromium-molybdenum alloy steel) |
| Alloy Type | Chromium-molybdenum (chrome-moly) hardenable alloy steel |
| Heat Condition | Annealed or normalized and tempered |
| Size | 1/2″ NB to 24″ NB (DN 15 to DN 600); larger to ASME B16.47 |
| Class / Rating | 150#, 300#, 600#, 900#, 1500#, 2500# · 3000#, 6000#, 9000# (socket-weld / threaded) |
| Pressure Ratings | PN 6 – PN 400 (PN6, 10, 16, 25, 40, 64, 100, 160, 250, 320, 400) |
| Related Specs | Pipe ASTM A335 P21; fittings ASTM A234 WP21; plate A387 Gr21 |
| Dimensional Standards | ASME B16.5, ASME B16.47 (Series A & B), MSS SP-44, DIN EN 1092-1 |
| Flange Types | Weld Neck (WNRF), Slip-On (SORF), Blind, Socket Weld (SWRF), Lap Joint, Threaded / Screwed, Spectacle Blind, Long Weld Neck, Orifice, Plate |
| Flange Faces | Raised Face (RF), Flat Face (FF), Ring Type Joint (RTJ), Tongue & Groove (T&G) |
| Weld Filler | Matching 3Cr-1Mo low-hydrogen consumables, with preheat & PWHT |
| Testing | Hardness, hydrostatic, UT, MT/PT per spec; EN 10204 3.1 / 3.2 |
F21 is the 3Cr-1Mo member of the A182 chrome-moly family, sitting between F22 and F5. The ~3% chromium with ~1% molybdenum gives creep strength and resistance to high-temperature hydrogen attack for demanding hydroprocessing service.
| Element | ASTM A182 F21 |
|---|---|
| Carbon (C) | 0.05 – 0.15% |
| Manganese (Mn) | 0.30 – 0.60% |
| Silicon (Si) | 0.50% max |
| Chromium (Cr) | 2.65 – 3.35% |
| Molybdenum (Mo) | 0.80 – 1.06% |
| Phosphorus (P) | 0.030% max |
| Sulphur (S) | 0.030% max |
| Mechanical Property | ASTM A182 F21 |
|---|---|
| Tensile Strength (min) | 75 ksi (515 MPa) |
| Yield Strength (min) | 45 ksi (310 MPa) |
| Elongation (min) | ~20% |
| Hardness | ≤ 207 HBW (typical) |
| Service Temperature | Sustained high temperature, ~600–650°C |
| Condition | Annealed or normalized & tempered |
| Product Form | 3Cr-1Mo Designation |
|---|---|
| Forgings / Flanges | ASTM A182 F21 |
| Seamless Pipe | ASTM A335 P21 |
| Fittings | ASTM A234 WP21 |
| Plate | ASTM A387 Gr 21 |
| Common name | 3Cr-1Mo Chrome-Moly Alloy Steel |
F21 Weld Neck Flange (WNRF)
F21 Slip-On Flange (SORF)
F21 Blind Flange
| Flange Type | Description & F21-Specific Use |
|---|---|
| Weld Neck (WNRF) | Tapered hub butt-welded to pipe for high-integrity, high-pressure hydroprocessing piping; weld with matching 3Cr-1Mo filler, preheat & PWHT. |
| Slip-On (SORF) | Fillet-welded over the pipe; used in chrome-moly piping at moderate pressure. |
| Blind | Seals pipe ends and vessel nozzles in high-temperature hydrogen and hydrocarbon systems. |
| Socket Weld (SWRF) | Small-bore (1/2″–2″) instrument and branch connections in hot service. |
| Lap Joint (LJRF) | Used with an F21 stub end where frequent dismantling is required. |
| Threaded (TRFF) | Internal NPT/BSP threads for non-welded connections. |
| Spectacle Blind / Long Weld Neck | Isolation spades and nozzle/long-neck flanges in A182 F21 for high-temperature duty. |
| Property | F21 | F22 | F11 | F5 |
|---|---|---|---|---|
| Nominal type | 3Cr-1Mo | 2.25Cr-1Mo | 1.25Cr-0.5Mo | 5Cr-0.5Mo |
| Chromium | ~3% | ~2.25% | ~1.25% | ~5% |
| Tensile (min) | 75 ksi | 75 ksi | 70 ksi | 70 ksi |
| Hydrogen-attack resistance | Good (above F22) | Good | Moderate | High |
| Typical role | Hydroprocessing / high-temp hydrogen | Hydrogen / high-temp | Boiler / moderate temp | Hot refinery sulphur |
3% chromium gives good resistance to high-temperature hydrogen attack for hydroprocessing reactors and piping per API 941.
Molybdenum gives strong creep resistance for sustained hot service to ~600–650°C.
Fills the chromium gap between the common F22 and F5 grades for specific hydroprocessing requirements.
Backed by matching pipe (A335 P21), fittings (A234 WP21) and plate (A387 Gr21) for full chrome-moly systems.
| Industry | Typical Application |
|---|---|
| Oil Refining | Hydrocracker and hydrotreater reactor and hot-piping flanges |
| Hydrogen / Hydroprocessing | High-temperature, high-pressure hydrogen-service flanges per API 941 |
| Petrochemical | Elevated-temperature hydrocarbon process flanged connections |
| Power Generation | High-temperature boiler and steam-line flanges |
| Heaters & Furnaces | Fired-heater and transfer-line flanged connections |
| Process Plant | General high-temperature chrome-moly piping flanges |
Made from certified 3Cr-1Mo with PMI verification of chromium and molybdenum — full chemistry and heat-treatment on the MTC.
Supplied annealed or normalized-and-tempered, with hardness within spec for weldability and hydrogen service.
WNRF, SORF, blind, socket-weld, threaded, lap-joint, spectacle, LWN, orifice and plate — in RF, FF, RTJ and T&G.
EN 10204 3.1 / 3.2 MTC with hardness results, heat/lot traceability, hydrostatic and third-party inspection on request.
A182 F21 flange prices reflect the 3% chromium chrome-moly alloy content plus forging and heat treatment — a specialised grade for high-temperature hydrogen and hydroprocessing service. Tesco Steel & Engineering offers competitive ex-works pricing from Mumbai with full export documentation and material traceability. Click Ask for Quote or message us on WhatsApp at +91 92233 66922 with flange type, size (NB), pressure class, quantity and documentation requirements.
Q1. What is an ASTM A182 F21 flange?
An ASTM A182 F21 flange is a forged chromium-molybdenum (chrome-moly) alloy steel flange with about 3% chromium and 1% molybdenum (3Cr-1Mo). The chromium and molybdenum give strong creep strength, elevated-temperature strength and resistance to high-temperature hydrogen attack, placing F21 between F22 (2.25Cr) and F5 (5Cr) for high-temperature, high-pressure hydrogen and hydroprocessing service. Flanges are made to ASTM A182 and machined to ASME B16.5 / B16.47 dimensions.
Q2. What is the chemical composition of ASTM A182 F21?
ASTM A182 F21 nominal composition: carbon 0.05–0.15%, manganese 0.30–0.60%, silicon 0.50% max, chromium 2.65–3.35%, molybdenum 0.80–1.06%, phosphorus 0.030% max, sulphur 0.030% max. The ~3% chromium with ~1% molybdenum is the defining 3Cr-1Mo chrome-moly composition.
Q3. What is F21 alloy steel used for?
ASTM A182 F21 (3Cr-1Mo) is used for high-temperature, high-pressure service in oil refineries and petrochemical plants, particularly hydroprocessing (hydrocracker and hydrotreater) reactors and hot piping where resistance to high-temperature hydrogen attack and good creep strength are needed. Its 3% chromium sits between the common F22 and F5 grades.
Q4. What is the difference between A182 F21, F22, F11 and F5?
These are chrome-moly alloy steels with increasing chromium: F11 is 1.25Cr-0.5Mo, F22 is 2.25Cr-1Mo, F21 is 3Cr-1Mo, and F5 is 5Cr-0.5Mo. F21 sits just above F22 in chromium, used for high-temperature hydrogen and hydroprocessing service; F5 and F9 go higher for hotter, more sulphidic streams. Grade selection follows the service temperature, hydrogen partial pressure and corrosivity.
Q5. Do A182 F21 flanges need post-weld heat treatment?
Yes. As a hardenable chrome-moly alloy steel, F21 requires preheat (typically around 200–300 degrees C) before welding and post-weld heat treatment (PWHT, a temper around 690–740 degrees C) to relieve stress, temper the heat-affected zone and restore toughness. Matching low-hydrogen consumables and controlled interpass temperature are used.
Q6. What standards apply to A182 F21 flanges?
A182 F21 flanges are forged to ASTM A182/A182M (Grade F21) and machined to ASME B16.5 (1/2 inch to 24 inch) or ASME B16.47 / MSS SP-44 for larger sizes, with EN 1092-1 for PN-rated flanges. Material is supplied annealed or normalized-and-tempered with EN 10204 3.1 / 3.2 certification. Matching pipe is ASTM A335 P21, fittings ASTM A234 WP21, plate A387 Gr21.
Q7. What are the mechanical properties of A182 F21?
Typical ASTM A182 F21 properties: tensile strength 75 ksi (515 MPa) minimum, yield strength 45 ksi (310 MPa) minimum, elongation about 20% minimum, hardness generally below 207 HBW. It is supplied in the annealed or normalized-and-tempered condition with strong elevated-temperature and creep properties.
Q8. What temperature can A182 F21 flanges handle?
A182 F21 is used for sustained high-temperature service, commonly up to about 600–650 degrees C, with good creep strength and resistance to high-temperature hydrogen attack at elevated hydrogen partial pressures. The exact allowable temperature and pressure follow the applicable code (e.g. ASME B16.5 / B31.3) and API 941 (Nelson curve) guidance.
Q9. What industries use A182 F21 flanges?
ASTM A182 F21 flanges are used in oil refining (hydrocracking and hydrotreating reactors and hot piping), petrochemical processing, power generation, and high-temperature hydrogen-service plant where 3Cr-1Mo creep strength and hydrogen-attack resistance are required.
Q10. Are A182 F21 flanges supplied with material test certificates?
Yes. Every A182 F21 flange is supplied with EN 10204 3.1 (or 3.2) mill test certificates confirming chemistry, mechanical properties, heat-treatment condition and heat/lot traceability, with hardness, hydrostatic testing and third-party inspection on request. Tesco Steel & Engineering is an ISO 9001:2015 certified manufacturer and exporter from Mumbai, India.