ASTM A182 F5 Weld Neck Flanges — 5Cr-1/2Mo Alloy Steel
Tesco Steel & Engineering forges ASTM A182 F5 weld neck flanges in 5% chromium, 0.5% molybdenum alloy steel — UNS K41545, Werkstoff Nr. 1.7362 — from 1/2″ NB to 56″ NB, in ASME B16.5 Class 150–2500 and European PN patterns. This is the refinery grade: chromium buys oxidation and sulphidation resistance in hot, H2S-bearing hydrocarbon streams, molybdenum buys creep strength to ~600 °C — the alloy of crude units, hydrotreaters, FCC circuits and fired heater manifolds, mating A335 P5 pipe. Normalized & tempered, hardness-controlled 143–217 HB, with PMI, NACE MR0175 and EN 10204 3.1/3.2 on request. ISO 9001:2015, made in Mumbai, India — exported worldwide.
A182 F5 · UNS K41545 · 1.7362
5Cr – 1/2Mo Refinery Grade
1/2″ – 56″ NB
Class 150 – 2500 · PN 2.5 – 400
Creep Strength to ~600 °C
NACE MR0175 · PMI · 3.1/3.2
ISO 9001:2015 · Exported Worldwide
ASTM A182 F5 Weld Neck Flange — 5Cr-1/2Mo Alloy Steel, Black Coated
What is an ASTM A182 F5 Weld Neck Flange?
ASTM A182 F5 is the 5Cr-1/2Mo alloy steel forging grade (UNS K41545) — the material refineries specify when hot hydrocarbon streams carry sulphur compounds that eat carbon steel. An F5 weld neck flange pairs that chemistry with the strongest flange design: a long tapered hub butt-welded to the pipe, bore matched to the pipe schedule, joint fully radiographable — built for crude units, hydrotreaters and fired heater circuits to ~600 °C.
The chemistry splits the work: 5% chromium forms a protective scale against high-temperature oxidation and sulphidation — the attack mode of hot H2S-bearing streams — while 0.5% molybdenum supplies creep strength, so the joint carries load for years at temperatures where carbon steel slowly stretches. The weld neck geometry adds its usual insurance: gradual stress transfer through the hub, a flush bore with no turbulence pocket, and a butt weld that radiographs cleanly.
F5 sits in the middle of the chrome-moly ladder we forge end to end: F11 and F22 for power-plant steam, F5 and F9 for sulphur-bearing refinery duty, and F91 for maximum creep strength. Its system partners are A335 P5 pipe and A234 WP5 fittings — one chemistry across the whole line.
Also searched as: A182 F5 WNRF flange, SA182 F5 weld neck flange, 5Cr-0.5Mo flange, UNS K41545 flange, 1.7362 flange, alloy steel F5 flange — all refer to the product on this page.
Chemical Composition of ASTM A182 F5
| C | Mn | P | S | Si | Ni | Cr | Mo |
|---|
| 0.15 max | 0.30-0.60 | 0.030 max | 0.030 max | 0.50 max | 0.50 max | 4.00-6.00 | 0.44-0.65 |
Values in weight %. The 4–6% chromium band centres on the nominal 5% that gives the grade its sulphidation resistance; the low 0.15% carbon ceiling keeps the air-hardening tendency manageable for welding — with preheat and PWHT still mandatory.
Mechanical Properties of ASTM A182 F5
| Tensile Strength, MPa [ksi] | Yield Strength, Min, MPa [ksi] | Elongation % min. | Reduction of Area % min. | Hardness HB |
|---|
| 485 [70] | 275 [40] | 20 | 35 | 143-217 |
Note the hardness range — a floor and a ceiling. The band confirms correct heat treatment (normalized & tempered or annealed), keeps the flange weldable, and holds it under the NACE MR0175 sour-service limit. Each flange's actual hardness is reported on the certificate.
Equivalent Grades of ASTM A182 F5
| Standard | Werkstoff Nr. | UNS | DIN |
|---|
| Alloy F5 | 1.7362 | UNS K41545 | 12CrMo195 |
The same 5Cr-1/2Mo chemistry runs through the whole piping system: A335 P5 seamless pipe, A234 WP5 butt-weld fittings and A217 C5 castings. An enquiry in any of these designations is quoted as the same material.
ASTM A182 F5 Weld Neck Flange Specifications
| ASTM A182 F5 Weld Neck Flanges are available in the following specifications: |
|---|
| Size | 1/2"NB to 56"NB |
| Class | 150#, 300#, 400#, 600#, 900#, 1500#, 2500# |
| Sch (Schedule) | XS, XXS, STD & Schedule 20, 40, 80, 160 |
| Pressure Ratings | PN 2.5 - PN 400 |
| Standards | ASME B16.5, ASME B16.47, EN 1092-1 Type 11, DIN 2631–2635, BS 4504 |
| Heat Treatment | Normalized & Tempered or Annealed, hardness 143–217 HB |
| Other Services | Hot Dip Galvanized (GI) ASTM A182 F5 Weld Neck Flanges
Sand Blasting on ASTM A182 F5 Weld Neck Flanges
Shot Peening on ASTM A182 F5 Weld Neck Flanges
Epoxy Coating on ASTM A182 F5 Weld Neck Flanges
FBE Coating on ASTM A182 F5 Weld Neck Flanges |
Why F5 for Hot Refinery Flanged Joints
Sulphidation Resistance
5% chromium builds a protective scale against the hot H2S attack that thins carbon steel in crude, vacuum and hydrotreater circuits — the reason F5 exists.
Creep Strength to ~600 °C
Molybdenum lets the joint carry pressure for years at heater-outlet temperatures where plain carbon steel would slowly stretch and thin.
Hardness Under Control
The specified 143–217 HB band certifies the heat treatment, keeps welds sound and holds the flange inside NACE MR0175 sour-service limits.
One Chemistry, Whole System
F5 flanges, A335 P5 pipe, WP5 fittings — matched chemistry and matched welding procedures from header to heater and back.
A Weld You Can Prove
The full-penetration butt weld radiographs cleanly — and with the preheat and PWHT this grade demands, proof matters twice as much.
Welding F5 — What the Grade Demands
F5 is air-hardening: the heat-affected zone of a weld quenches itself to brittle martensite even in still air. Sound joints follow three rules — preheat around 200 °C, matching 5Cr-1/2Mo consumables (E8018-B6 / ER80S-B6, the old E502 class), and mandatory PWHT at roughly 700–760 °C to temper the HAZ and relieve stress. Plan the PWHT into the construction schedule from day one.
Do not skip PWHT. An as-welded F5 joint carries a hard, crack-prone heat-affected zone; ASME B31.3 mandates post-weld heat treatment for this material class in essentially all thicknesses.
Where ASTM A182 F5 Weld Neck Flanges Are Used
Refineries are home ground: crude and vacuum distillation transfer lines, fired heater headers and crossover manifolds, hydrotreater and hydrocracker loops, FCC and coker piping — every hot circuit where sulphur compounds ride along with the hydrocarbons. Petrochemical furnaces and high-temperature auxiliaries take the grade for the same reasons. Below the sulphidation threshold, A105 is the economical choice; for more severe sulphur attack, F9 steps up; for supercritical steam creep duty, F91 tops the ladder — all forged in-house.
Production & Packing
Certified 5Cr-1/2Mo blanks are forged, normalized and tempered, hardness-surveyed, then CNC-turned: hub profiled, bore matched to your pipe schedule, weld end bevelled to 37.5°, faces serrated, and each flange marked with grade, size, rating and heat number. PMI verifies the chromium on the finished part. The crate below is a shipped F5 order — black-coated flanges, face-protected, on lined seaworthy packing:
A182 F5 Alloy Steel Flanges — Lined Wooden Export Crate, Ready for Dispatch
ASTM A182 F5 Weld Neck Flange Dimensions
F5 weld neck flanges share their dimensions with every other material in the same class — OD, thickness, hub, bore, bolt circle and bolting per the standard tables. Full ASME B16.5 charts:
European PN dimensions are published on the EN 1092-1 Type 11, DIN 2631–2635 and BS 4504 pages.
Price List & How to Order
F5 pricing follows the alloy steel market plus heat-treatment and testing scope, so we quote live rather than publish a static list. Common refinery sizes move quickly at competitive export prices. To get a firm quotation, usually within 24 hours:
1
List your requirement — size (NB), class or PN, standard (ASME B16.5 / B16.47 / EN / DIN / BS), facing (RF or RTJ), pipe schedule or bore, and quantity.
2
Add any extras — NACE MR0175, PMI, 3.2 certification, or a specific heat treatment condition.
ASTM A182 F5 Weld Neck Flanges — Frequently Asked Questions
What is an ASTM A182 F5 weld neck flange?
It is a weld neck flange forged from ASTM A182 grade F5 — the 5% chromium, 0.5% molybdenum alloy steel (UNS K41545). The long tapered hub is butt-welded to the pipe with the bore matched to the pipe schedule, giving a radiographable, fatigue-resistant joint in the alloy refineries reach for when hot, sulphur-bearing hydrocarbons make plain carbon steel corrode and scale: crude and vacuum units, hydrotreaters and fired heater circuits.
What does 5Cr-1/2Mo mean, and what does each element do?
F5 contains nominally 5% chromium and 0.5% molybdenum. The chromium forms a protective oxide that resists high-temperature oxidation and — critically for refineries — sulphidation by hot H2S-bearing streams, roughly in proportion to its content. The molybdenum provides creep strength, letting the steel carry load for years at temperatures where plain carbon steel would slowly stretch. Together they define the classic refinery alloy ladder from F5 up through F9.
What temperature can F5 flanges handle?
F5 works in continuous service to roughly 600 °C, with design stresses falling per the ASME rating tables as temperature climbs. Below about 425 °C, cheaper carbon steel A105 usually does the job unless sulphidation is the driver; above F5's comfort zone, the ladder continues to F9 (9Cr-1Mo) for more sulphidation resistance and F91 (modified 9Cr) for maximum creep strength. Where the stream is hot AND sulphur-rich, F5 earns its keep well below its temperature ceiling.
How does F5 compare with F11, F22, F9 and F91?
Think of chromium content as the sulphidation dial and molybdenum/vanadium as the creep dial. F11 (1.25Cr-0.5Mo) and F22 (2.25Cr-1Mo) are the power-plant steam grades — strong, but light on chromium. F5 (5Cr) and F9 (9Cr-1Mo) are the refinery grades, trading a little strength for much better resistance to hot sulphur attack. F91 (modified 9Cr-1Mo-V) tops the ladder for creep strength in supercritical steam. We forge weld neck flanges in all of them.
What are the equivalent designations for A182 F5?
UNS K41545; Werkstoff Nr. 1.7362; and the DIN designation 12CrMo19-5. In piping systems it runs alongside A335 P5 seamless pipe, A234 WP5 butt-weld fittings and A217 C5 castings — the same 5Cr-1/2Mo chemistry across every product form. An enquiry in any of these designations is quoted as the same material.
What is the chemical composition of ASTM A182 F5?
Carbon 0.15% max, manganese 0.30 to 0.60%, phosphorus 0.030% max, sulphur 0.030% max, silicon 0.50% max, nickel 0.50% max, chromium 4.00 to 6.00% and molybdenum 0.44 to 0.65%. The wide chromium band is deliberate — nominal 5% — and the low carbon keeps the air-hardening tendency manageable for welding.
What are the mechanical properties of A182 F5 flanges?
Minimum tensile strength 485 MPa (70 ksi), minimum yield strength 275 MPa (40 ksi), minimum elongation 20%, minimum reduction of area 35%, and hardness controlled within 143 to 217 HB. Note that hardness has both a floor and a ceiling: the range confirms correct heat treatment, keeps the flange weldable, and holds it under sour-service limits.
Which pipe grade do F5 weld neck flanges mate with?
ASTM A335 P5 — the 5Cr-1/2Mo seamless alloy pipe that shares F5's chemistry and heat treatment philosophy. A234 WP5 fittings complete the system. The weld neck bore is machined to the pipe schedule you state, so the bore runs flush through the joint, and the bevel arrives ready for a matched-chemistry butt weld.
How are F5 flanges welded to pipe?
With matching 5Cr-1/2Mo consumables — E8018-B6 electrodes or ER80S-B6 wire (the old E502 classification) — plus the discipline the grade demands: preheat around 200 °C, controlled interpass temperature, and mandatory post-weld heat treatment at roughly 700 to 760 °C. F5 is air-hardening, so skipping preheat or PWHT leaves a brittle, crack-prone heat-affected zone. The 37.5 degree bevel comes machined ready for a radiographable butt weld.
Why is PWHT mandatory for F5 flange welds?
Because 5% chromium makes the steel air-hardening: the heat-affected zone of a weld quenches itself to hard, brittle martensite even in still air. Post-weld heat treatment tempers that zone back to a tough, stable structure and relieves residual stress. ASME B31.3 mandates PWHT for this material class in essentially all thicknesses — plan it into the construction schedule from day one.
Where are ASTM A182 F5 weld neck flanges used?
Refineries above all: crude and vacuum distillation transfer lines, fired heater headers and manifolds, hydrotreater and hydrocracker circuits, FCC and coker piping — anywhere hot hydrocarbon streams carry sulphur compounds that eat carbon steel. F5 also appears in petrochemical furnaces and high-temperature steam auxiliaries where its balance of creep strength and scaling resistance fits the duty.
What sizes and standards do you manufacture F5 weld neck flanges in?
From 1/2 inch NB to 56 inch NB: ASME B16.5 Class 150 to 2500 up to 24 inch, ASME B16.47 above, and European PN 2.5 to PN 400 patterns to EN 1092-1 Type 11, DIN and BS 4504. Raised face is standard, ring joint for high-class refinery service on request, and every bore is machined to the mating pipe schedule from Sch 20 through XXS.
Are F5 flanges available for sour service (NACE)?
Yes. The specified 217 HB hardness ceiling keeps properly heat-treated F5 within NACE MR0175 / ISO 15156 limits, and hot sour hydrocarbon service is precisely the grade's natural habitat. We certify NACE compliance on request, run hardness surveys across the flange, and document everything on the EN 10204 3.1 or 3.2 certificate.
What testing and certification do you supply with F5 flanges?
Every lot ships with EN 10204 3.1 mill test certificates covering chemical analysis, mechanical properties, heat treatment condition and hardness, with 3.2 certification witnessed by Lloyd's, DNV, BV or TÜV on request. We also offer PMI — essential for alloy grades, so the 5% chromium is verified on the actual flange — ultrasonic and magnetic particle examination, and full heat-number traceability from billet to finished part.
Do you keep A182 F5 weld neck flanges in stock? What is the lead time?
Common refinery sizes in Class 150, 300 and 600 are frequently available from stock or short production runs — the crate photograph on this page is a shipped F5 order. Larger diameters, Class 900 to 2500 and special heat treatment conditions are forged to order, typically in 3 to 5 weeks depending on size and quantity. Send your list for a firm delivery commitment.
What information should I include in an F5 flange enquiry?
Six things: size (NB), pressure class or PN rating, dimensional standard (ASME B16.5, B16.47 or EN/DIN/BS), facing (RF or RTJ), pipe schedule or bore, and quantity. Add any extras — NACE compliance, PMI, 3.2 certification, specific heat treatment condition. With these details we return a firm quotation, usually within 24 hours.
Do you export ASTM A182 F5 flanges outside India?
Yes. Tesco Steel & Engineering is an ISO 9001:2015 certified manufacturer based in Mumbai, and F5 weld neck flanges ship regularly to refineries, EPC contractors and stockists across the Middle East, Europe, Africa, Southeast Asia and the Americas. Flanges travel face-protected in lined wooden crates — as photographed on this page — with full heat-number and heat-treatment traceability.
