Stainless Steel F6b
UNS S41026 · ASTM A182 Gr F6b
F6b is a martensitic stainless forging grade (UNS S41026, ASTM A182 Gr F6b) chemically close to 410 but ordered to the A182 forged-product specification for pressure parts.
Reference datasheet — F6b is not in the instant-quote catalog. Upload your part and an engineer will quote it in this grade or suggest the closest stocked equivalent.
Values for the QT condition
F6b tempers and conditions
F6b is supplied in 4 conditions, soft to hard. QT is the default FabDigit quotes; the values on this page are for it.
Compare all 4 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Annealed | Pick for rough machining, deep hole drilling or cold straightening before final quench-and-temper; not a code-qualified delivery condition for A182 F6b. | 320 | 540 | 28 | 175 HB | — |
Normalized and tempered | Air-cooled route used on very heavy forgings where oil quenching risks cracking; slightly lower strength and toughness scatter than full Q&T. | 600 | 780 | 20 | 24 HRC | 3 % IACS |
QTDefault Quenched and tempered | Standard stocked condition for F6b flanges, valve bodies and fittings — meets the 110 ksi / 90 ksi minimum with balanced toughness. | 660 | 810 | 20 | 26 HRC | — |
Q&T high-strength | Ordered when the fitting must match a 130 ksi class body or trim; higher strength at the cost of impact toughness and SSC resistance — not for sour service. | 800 | 950 | 16 | 31 HRC | — |
What is F6b?
F6b is a martensitic stainless forging grade (UNS S41026, ASTM A182 Gr F6b) chemically close to 410 but ordered to the A182 forged-product specification for pressure parts. It is used for forged flanges, valve bodies and fittings in annealed, normalized-and-tempered and quenched-and-tempered conditions, with default values near 660 MPa yield, 810 MPa tensile, 20 % elongation and 265 HB (26 HRC) and service to 480 °C. Machinability is moderate (score 42), corrosion resistance (45) suits mild process media only, and welds need preheat plus a post-weld temper; 415 (CA6NM) is the alternative where weld toughness governs. F6b has a density of 7.75 g/cm³ (0.28 lb/in³), lighter than 65% of stainless steel grades. It melts at 1,480°C (2,696 °F). F6b has a yield strength of 660 MPa (95.7 ksi) and a tensile strength of 810 MPa (117 ksi) — stronger than 91% of stainless steel grades. Elongation at break is 20% and the elastic modulus is 200 GPa (29 Msi).
What is F6b used for?
- forged flanges
- valve bodies
- fittings
Advantages
- High electrical conductivity — 3 % IACS, better than 95% of stainless steel grades
- High strength — 660 MPa (95.7 ksi), better than 91% of stainless steel grades
- Low embodied carbon — 3.4 kg CO₂/kg, better than 91% of stainless steel grades
- Conducts heat well — 24.9 W/m·K (14.4 BTU/hr·ft·°F), better than 87% of stainless steel grades
Limitations
- Difficult to weld — 35/100, worse than 86% of stainless steel grades
- Needs corrosion protection — 45/100, worse than 85% of stainless steel grades
- Low fracture toughness — 75 MPa·√m (68.3 ksi·√in), worse than 81% of stainless steel grades
- Limited ductility — 20%, worse than 79% of stainless steel grades
- Limited formability — 25/100, worse than 78% of stainless steel grades
F6b properties
Typical room-temperature values for F6b-QT; bars are the position among stainless steel grades.
Physical3
F6b has a density of 7.75 g/cm³ (0.28 lb/in³), lighter than 65% of stainless steel grades. It melts at 1,480°C (2,696 °F).
Mechanical16
F6b has a yield strength of 660 MPa (95.7 ksi) and a tensile strength of 810 MPa (117 ksi) — stronger than 91% of stainless steel grades. Elongation at break is 20% and the elastic modulus is 200 GPa (29 Msi).
Thermal6
F6b is rated for continuous service to 480°C (896 °F). It conducts heat at 24.9 W/m·K (14.4 BTU/hr·ft·°F), better than 87% of stainless steel grades. Thermal expansion is 9.9 µm/m·K (5.5 µin/in·°F).
Electrical3
F6b conducts electricity at 3 % IACS, better than 95% of stainless steel grades.
Chemical & Environmental3
Corrosion resistance is fair (45/100), worse than 85% of stainless steel grades.
Sustainability4
Producing a kilogram of F6b takes about 46 MJ of energy and emits 3.4 kg of CO₂ — less than 88% of stainless steel grades. Typical recycled content is 60%.
Manufacturability6
F6b's machinability is fair (42/100, better than 79% of stainless steel grades); weldability fair (35/100); formability poor (25/100).
Common Calculations5
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the stainless steel family
Yield strength against density for every stainless steel grade FabDigit runs. F6b is highlighted; hover a dot for its name, or open the interactive family chart.
Working with F6b
Is F6b easy to machine?
Machine in the annealed state where possible; in Q&T condition use rigid setups, sharp carbide, moderate speed (~60–90 m/min) and heavy positive feeds to avoid work-hardened glazing.
Can F6b be welded?
Weldable with 410/410NiMo or austenitic 309 filler but requires 200–300 °C preheat, controlled interpass and a 650–760 °C post-weld temper to avoid untempered-martensite cracking.
Can F6b be formed, bent or molded?
Hot forge at 1150–1200 °C, finish above ~900 °C and slow-cool or anneal immediately; cold forming is limited to minor straightening in the annealed condition.
F6b chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| C | ≤ 0.15 | 0.1 |
| Mn | ≤ 1 | 0.6 |
| Si | ≤ 1 | 0.4 |
| P | ≤ 0.02 | 0.02 |
| S | ≤ 0.02 | 0.01 |
| Cr | 11.5 – 13.5 | 12.5 |
| Niimproves hardenability and toughness vs plain 410 | 1 – 2 | 1.5 |
| Mo | 0.4 – 0.6 | 0.5 |
| Fe | balance |
What surface finishes work on F6b?
Takes a good mechanical/electro-polish and passivates in nitric acid; hard chrome or nitriding is used for wear faces — avoid electroplating without hydrogen bake-out above 28 HRC.
Surface treatments FabDigit runs on stainless steel parts — pick them in the quote configurator or call them out on the drawing. Each links to its datasheet in the surface-finish library (thickness, specs, call-out, material verdicts).
Passivation
Organic Coating
Thermal Spray
Equivalent designations
Standards and trade names that resolve to Stainless Steel F6b in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- UNS
- S41026
- ASTM
- A182 Gr F6b
- Similar grades
- S41000
How much does F6b cost?
F6b is a premium-cost stainless steel ($$$), cheaper than about 51% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
F6b — frequently asked
What is F6b used for?
F6b is typically used for forged flanges, valve bodies and fittings. In short: ASTM A182 forging grade; flange and fitting 410; pressure-rated martensitic bar.
What is the yield strength of F6b?
F6b has a typical yield strength of 660 MPa (95.7 ksi) and a tensile strength of 810 MPa (117 ksi) — stronger than 91% of stainless steel grades. Strength varies by condition: see the 4 listed tempers.
Is F6b easy to machine?
Not especially — machinability is rated fair (42/100, better than 79% of stainless steel grades). Machine in the annealed state where possible; in Q&T condition use rigid setups, sharp carbide, moderate speed (~60–90 m/min) and heavy positive feeds to avoid work-hardened glazing.
Can F6b be welded?
With care — weldability is rated fair (35/100). Weldable with 410/410NiMo or austenitic 309 filler but requires 200–300 °C preheat, controlled interpass and a 650–760 °C post-weld temper to avoid untempered-martensite cracking.
What surface finishes work on F6b?
Takes a good mechanical/electro-polish and passivates in nitric acid; hard chrome or nitriding is used for wear faces — avoid electroplating without hydrogen bake-out above 28 HRC.
Can F6b be formed, bent or molded?
Hot forge at 1150–1200 °C, finish above ~900 °C and slow-cool or anneal immediately; cold forming is limited to minor straightening in the annealed condition.
What is the maximum service temperature of F6b?
F6b is rated for continuous use to about 480°C (896 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between F6b-QT and F6b-ANN?
QT is the default condition — standard stocked condition for F6b flanges, valve bodies and fittings — meets the 110 ksi / 90 ksi minimum with balanced toughness. ANN: pick for rough machining, deep hole drilling or cold straightening before final quench-and-temper; not a code-qualified delivery condition for A182 F6b. Yield strength is 660 MPa in QT versus 320 MPa in ANN.
How much does F6b cost?
F6b is a premium-cost stainless steel ($$$), cheaper than about 51% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Sources
- ASTM A182/A182M — Forged or Rolled Alloy and Stainless Steel Pipe Flanges, Fittings, Valves and Parts — ASTM International (2023)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
- ASM Specialty Handbook — Stainless Steels — ASM International (1994)
- NACE MR0175 / ISO 15156-3 — Cracking-resistant CRAs for H₂S service — NACE/ISO (2015)
- GB/T 1220 (1Cr13/2Cr13 ) — SAC (2007)
Property data is compiled from published supplier and standards handbooks and normalised for comparison; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.