What Is ASTM A182 F11?
ASTM A182 F11 is a chromium-molybdenum (Cr-Mo) low-alloy steel grade defined within ASTM A182 / A182M — the Standard Specification for Forged or Rolled Alloy and Stainless Steel Pipe Flanges, Forged Fittings, and Valves and Parts for High-Temperature Service. The "F11" designation identifies it as a 1.25% chromium / 0.5% molybdenum alloy — part of the Cr-Mo steel family that engineers have relied upon for high-pressure, high-temperature service for more than seven decades.
The alloy is produced as forged or rolled product, including open die forgings, seamless rolled rings, valve bodies, flanges, and custom ASTM A182 F11 forged parts. Its equivalent ASME specification is ASME SA182 / SA182M F11, which carries identical chemical and mechanical requirements and is used in code-stamped pressure vessel and piping systems under the ASME Boiler and Pressure Vessel Code (BPVC). Its equivalent ASME specification is ASME SA182 / SA182M F11, which carries identical chemical and mechanical requirements and is used in code-stamped pressure vessel and piping systems under the ASME Boiler and Pressure Vessel Code (BPVC).
Why Cr-Mo matters: Chromium increases hardenability, oxidation resistance, and corrosion resistance at elevated temperatures. Molybdenum raises creep strength and temper resistance. Together, they make F11 significantly stronger than carbon steel at temperatures above 400 °C — without the cost or weldability penalty of higher-alloy grades like F22 or F91.
Unlike stainless steel, F11 does not contain enough chromium (the minimum threshold is 10.5%) to be self-passivating. It is a low-alloy pressure steel optimized for elevated-temperature mechanical performance, not for aqueous corrosion resistance. In dry, high-temperature gas service — refinery furnace tubes, steam lines, heat exchangers — it is often the most cost-effective engineering choice available.
ASTM A182 F11 Chemical Composition
The table below shows the required chemical composition (weight %) per ASTM A182 for Grade F11. All figures are maximum unless otherwise noted. The Cr and Mo ranges are identical across all three classes — what differentiates the classes is the heat treatment applied and the resulting mechanical properties, not the base chemistry.
| Element | Symbol | Class 1 (wt%) | Class 2 (wt%) | Class 3 (wt%) | Role in Alloy |
|---|---|---|---|---|---|
| Carbon | C | 0.05 – 0.15 | 0.05 – 0.15 | 0.10 – 0.20 | Base strength, hardenability |
| Manganese | Mn | 0.30 – 0.80 | 0.30 – 0.80 | 0.30 – 0.80 | Deoxidation, toughness |
| Phosphorus | P | 0.040 max | 0.040 max | 0.040 max | Controlled impurity |
| Sulfur | S | 0.040 max | 0.040 max | 0.040 max | Controlled impurity |
| Silicon | Si | 0.50 – 1.00 | 0.50 – 1.00 | 0.50 – 1.00 | Oxidation resistance |
| Chromium | Cr | 1.00 – 1.50 | 1.00 – 1.50 | 1.00 – 1.50 | High-temp strength, oxidation |
| Molybdenum | Mo | 0.44 – 0.65 | 0.44 – 0.65 | 0.44 – 0.65 | Creep resistance, strength |
The silicon content (0.50–1.00%) is notably higher than most plain carbon steels, contributing meaningfully to high-temperature oxidation resistance — a key reason F11 performs well in steam and hot gas service where surface scaling is a concern. The carbon range in Class 3 (0.10–0.20%) is slightly higher than Classes 1 and 2, enabling greater hardenability when quenched before tempering.
F11 Class 1 vs Class 2 vs Class 3: Which Should You Specify?
ASTM A182 F11 is available in three strength classes. Each is produced from the same base alloy chemistry but with different heat treatment cycles that yield progressively higher tensile properties. Your class selection should be driven by the design stress requirements of the component — not by a preference for the highest strength by default.
| Property | Class 1 | Class 2 ★ Most Common | Class 3 |
|---|---|---|---|
| Min Tensile Strength | 415 MPa / 60 ksi | 515 MPa / 75 ksi | 620 MPa / 90 ksi |
| Min Yield Strength | 205 MPa / 30 ksi | 310 MPa / 45 ksi | 415 MPa / 60 ksi |
| Min Elongation (2 in) | 20% | 20% | 20% |
| Min Reduction of Area | 35% | 35% | 35% |
| Heat Treatment | Annealed | Normalized + Tempered | Quenched + Tempered |
| Weldability | Best | Good | Moderate |
| Typical Applications | Low-pressure fittings | Flanges, valve bodies | High-pressure components |
Practical note for procurement: Class 2 is by far the most commonly specified globally. It provides a balanced combination of weldability, toughness, and elevated-temperature strength that satisfies design requirements for most flanges, valve bodies, and pressure fittings. Specify Class 3 only when Class 2 yield strength is the limiting design factor in your stress calculation.
ASTM A182 F11 Mechanical Properties (Class 2)
The values below apply to Class 2 — the most widely specified grade — tested at room temperature per ASTM A182 requirements. Design engineers should apply appropriate elevated-temperature derating factors from ASME BPVC Section II, Part D for actual service conditions.
Elevated-Temperature Performance
A critical characteristic of F11 that room-temperature tables don't fully convey is its creep and stress-rupture behavior at service temperatures. At 500 °C, F11 retains approximately 60–65% of its room-temperature tensile strength — compared to roughly 40% for plain carbon steel. This temperature-dependent strength advantage is the primary engineering justification for specifying F11 over lower-cost carbon steel grades in steam and process systems operating above 370 °C.
Design note: For applications above 580 °C, the higher-alloy grades F22 (2.25Cr–1Mo) or F91 (9Cr–1Mo–V) should be evaluated. F11 does not provide adequate long-term creep resistance in continuous service above 593 °C. For complete mechanical test data, heat treatment records, and size capabilities for our F11 open die forgings and seamless rolled rings, see our product page.
Heat Treatment of ASTM A182 F11 Forgings
The heat treatment cycle determines which strength class the finished forging achieves. All three processes begin with hot forging to refine the grain structure through plastic deformation, after which the thermal cycle is applied in controlled gas or electric furnaces.
Post-weld heat treatment (PWHT) at 680–760 °C is mandatory for F11 components after welding. Failure to perform PWHT can result in hydrogen-induced cracking and excessively hard heat-affected zones (HAZ) susceptible to stress corrosion cracking in sour service per NACE MR0175.
Key Applications of ASTM A182 F11 Forged Parts
F11 is a workhorse grade wherever sustained elevated temperatures and pressures combine with a need for cost-effective, proven alloy performance. The six industries below represent its primary global end uses, spanning upstream oil & gas through power generation and chemical processing.
ASTM A182 F11 vs F22: How to Choose the Right Cr-Mo Grade
The two most common Cr-Mo forging grades in high-temperature service are F11 (1.25Cr–0.5Mo) and F22 (2.25Cr–1Mo). Both are proven, code-qualified materials — but they serve different service windows, and specifying the wrong grade carries real cost and reliability consequences.
| Selection Criterion | F11 · 1.25Cr–0.5Mo | F22 · 2.25Cr–1Mo |
|---|---|---|
| Chromium Content | 1.00 – 1.50 % | 2.00 – 2.50 % |
| Molybdenum Content | 0.44 – 0.65 % | 0.87 – 1.13 % |
| Max Service Temperature | 593 °C (1100 °F) | 650 °C (1200 °F) |
| Creep Resistance | Good (sufficient <580 °C) | Superior (needed >540 °C) |
| Oxidation Resistance | Moderate | Good |
| Weldability | Good (lower Pcm) | Moderate (higher Pcm) |
| Relative Material Cost | ✓ Lower | ~15–25% higher |
| PWHT Required? | Yes — 680–760 °C | Yes — 690–760 °C |
| Hydrogen Attack Resistance | Limited (Nelson Curve) | Better (higher threshold) |
| NACE MR0175 Compliant? | Yes (with hardness control) | Yes (with hardness control) |
| Best For | CDU flanges, steam lines <540 °C | Hydrocrackers, reformers >538 °C |
Decision rule: If your design temperature is consistently below 540 °C, F11 delivers equivalent service life at lower cost with better weldability. If you are operating at or above 560 °C continuously — or if your process involves high-partial-pressure hydrogen (hydrogen attack risk per Nelson Curve) — specify F22 or evaluate F91. Over-specifying F22 in a 450 °C steam flange application is budget waste without performance benefit.
Welding ASTM A182 F11: Requirements and Best Practices
F11 is weldable with proper procedure qualification (PQR per ASME Section IX or AWS D1.1), but unlike carbon steel it requires pre-weld and post-weld thermal control to prevent hydrogen-induced cracking (HIC) and ensure the heat-affected zone (HAZ) meets mechanical property and hardness requirements.
Preheat Requirements
Per AWS D1.1 and ASME Section IX, preheat for F11 is typically 175–230 °C (350–450 °F) depending on section thickness and the hydrogen content of the welding process. Thicker sections and cellulosic electrodes demand the higher end of this range. Preheat must be maintained throughout the entire weld pass sequence — allowing the joint to cool to ambient between passes risks HAZ cracking.
Filler Metal Selection
Match the filler metal to the base material chemistry: use ER80S-B2 (GTAW/GMAW) or E8018-B2 (SMAW) low-hydrogen electrodes classified for 1.25Cr–0.5Mo service. Low-hydrogen electrodes must be re-dried and stored per manufacturer instructions — target diffusible hydrogen content below 4 mL/100g of weld metal (H4 designation). Verify that deposited weld metal chemistry produces a creep-matching microstructure after PWHT.
Post-Weld Heat Treatment (PWHT)
PWHT at 680–760 °C is mandatory for all pressure-retaining welds in F11 components per ASME B31.3, ASME BPVC Section I, and API 582. Hold time is typically 1 hour per 25 mm (1 in.) of section thickness, with a minimum hold time of 1 hour regardless of thickness. PWHT serves three critical functions: it tempers the martensitic HAZ to restore toughness, diffuses trapped hydrogen from the weld, and stress-relieves residual stresses that could drive environmentally assisted cracking in service.
Related Standards and Certifications for F11 Forgings
When specifying or procuring ASTM A182 F11 forged parts, the following standards and certifications may be applicable to your project. Not all are required for every application — consult your engineer of record and project specification to determine which are contractually binding.
| Standard / Certification | Issuing Body | Relevance to F11 Forgings | Typical Requirement |
|---|---|---|---|
| ASTM A182 / A182M | ASTM International | Primary material specification for F11 forgings | Mandatory for all F11 forgings |
| ASME SA182 / SA182M | ASME | BPVC code-equivalent of ASTM A182 | Required for ASME-stamped pressure equipment |
| ASTM A788 | ASTM International | General forging quality requirements | Often invoked by purchaser in addition to A182 |
| API 6A | API | Wellhead & Christmas tree material requirements | Forgings must meet API 6A material requirements; note: API 6A Monogram license is held by equipment assemblers, not forging suppliers |
| NACE MR0175 / ISO 15156 | NACE / ISO | Sour service (H₂S) material qualification | F11 can comply when supplied with hardness ≤22 HRC — compliance verified and documented on MTC |
| EN 10228-1 to -4 | CEN (Europe) | European forging NDT requirements | Invoked by European project purchasers |
| EN 10204 3.1 | CEN (Europe) | MTC issued and signed by manufacturer's QA department | Jiangsu Liangyi standard for every order — no extra charge |
| EN 10204 3.2 | CEN (Europe) | MTC co-signed by accredited third-party inspector | Available on request; TPI witness arranged separately — not a certificate Jiangsu Liangyi holds independently |
| PED 2014/68/EU | European Commission | EU pressure equipment directive | CE marking is the responsibility of the finished equipment assembler; F11 forgings can be supplied with PED-compliant material documentation on request |
| ISO 9001:2015 | ISO | Quality management system — certificate held by Jiangsu Liangyi | Our only independently held certificate; scope covers manufacture of forged steel products |
Buyer's Checklist: 10 Things to Verify Before Ordering F11 Forgings
Procurement teams ready to source F11 forgings can request a quote for ASTM A182 F11 forgings from Jiangsu Liangyi directly. Before placing any order — particularly with overseas manufacturers — verify the following ten points. Material non-conformances in Cr-Mo forgings are difficult and expensive to detect in the field after installation.
- Class Confirmation: Confirm whether your design specification calls for Class 1, 2, or 3. Do not assume Class 2 — check your piping line class or pipe specification sheet explicitly.
- Document Type (EN 10204 3.1 vs 3.2): EN 10204 3.1 is a manufacturer-issued MTC; EN 10204 3.2 requires an independent third-party inspector to witness and co-sign. The 3.2 document is mandatory for many European, Norwegian, and offshore projects — clarify this requirement before placing your order, as it affects scheduling and cost.
- Heat Treatment Records: Request actual heat treatment cycle records (furnace chart, temperature, dwell time, cooling method) as part of the MTC document package. These are not optional for any Cr-Mo forging.
- Chemical Analysis Verification: Confirm that the MTR's Cr and Mo values fall within the ASTM A182 F11 compositional ranges. Do not rely on a document that merely states "ASTM A182 F11" — verify the actual heat chemistry numbers. Substitution of lower-alloy steel is a known risk in commodity forging supply chains.
- Test Coupon Traceability: Verify that the mechanical test coupon was forged from the same heat of steel and heat-treated in the same furnace charge as the production pieces. Request the coupon location, orientation, and heat number.
- NDT Scope and Standard: Clarify whether ultrasonic testing (UT) is performed per ASTM A388 or a less stringent customer standard. For forgings with section thickness above 75 mm, UT is essential to detect internal laminar or dendritic defects not visible externally.
- Heat Treatment Condition on Delivery: Confirm the forgings are delivered in the correct heat-treated condition matching the specified class. Receiving Class 1 annealed product when Class 2 normalized-and-tempered was specified is a non-conformance that may not be visible without testing.
- Drawing Review and Dimensional Tolerances: Ensure engineering drawings state metric or imperial clearly, that tolerances are achievable on the manufacturer's equipment, and that first-article inspection (FAI) is scoped for new part numbers.
- ISO 9001:2015 Certification Scope: Verify the manufacturer holds a current ISO 9001:2015 certificate from an accredited third-party certification body (not self-declared) and that the certification scope explicitly covers the manufacture of forged steel products.
- Realistic Lead Time and Packaging: Confirm lead time accounts for the heat treatment cycle specific to the class ordered — Class 3 Q+T forgings require longer cycle times than Class 1 annealed. Also confirm corrosion protection and packing method for sea freight — bare Cr-Mo forgings are susceptible to surface rust during ocean transit.
ASTM A182 F11 — FAQ for Engineers and Buyers
These are the most common questions about ASTM A182 F11 received from engineers, purchasing managers, and quality inspectors globally. Answers are based on the current ASTM A182 standard and industry practice.
Ready to Source ASTM A182 F11 Forgings?
Jiangsu Liangyi has manufactured Cr-Mo alloy steel forgings for 27+ years. We supply F11 Class 1, 2, and 3 open die forgings and seamless rolled rings with EN 10204 3.1 MTC as standard (3.2 third-party witness available on request), 15–35 day lead times, and free technical review of your drawings.