Stainless Steel F6b QT-HS
Heat-treated state
UNS S41026 · ASTM A182 Gr F6b
QT-HS = 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.
Values for the QT-HS condition
Other F6b tempers and conditions
F6b is listed in 4 conditions; see the grade overview at F6b.
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 | — |
QT-HSThis page 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 QT-HS?
F6b QT-HS is F6b heat treated to QT-HS — 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. F6b QT-HS has a yield strength of 800 MPa (116 ksi) and a tensile strength of 950 MPa (138 ksi) — stronger than 96% of stainless steel grades. Elongation at break is 16% and the elastic modulus is 200 GPa (29 Msi). F6b QT-HS 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). QT is the default condition FabDigit quotes; QT-HS is available on request or by drawing note.
Advantages
- High strength — 800 MPa (116 ksi), better than 96% of stainless steel grades
- High electrical conductivity — 3 % IACS, better than 95% 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
- Limited ductility — 16%, worse than 88% of stainless steel grades
- 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 formability — 25/100, worse than 78% of stainless steel grades
F6b QT-HS properties
Typical room-temperature values for F6b QT-HS; 10 are specific to this condition. Other listed values are F6b reference data and may not represent this condition. Bars are the position among stainless steel grades.
Physical3
F6b QT-HS 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 QT-HS has a yield strength of 800 MPa (116 ksi) and a tensile strength of 950 MPa (138 ksi) — stronger than 96% of stainless steel grades. Elongation at break is 16% and the elastic modulus is 200 GPa (29 Msi).
Thermal6
F6b QT-HS 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 QT-HS 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 QT-HS 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 QT-HS's machinability is fair (35/100, better than 51% of stainless steel grades); weldability fair (35/100); formability poor (25/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with F6b QT-HS
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.
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.
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 | — |
F6b QT-HS — frequently asked
What is F6b QT-HS used for?
F6b QT-HS 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 QT-HS?
F6b QT-HS has a typical yield strength of 800 MPa (116 ksi) and a tensile strength of 950 MPa (138 ksi) — stronger than 96% of stainless steel grades. Strength varies by condition: see the 4 listed tempers.
Is F6b QT-HS easy to machine?
Not especially — machinability is rated fair (35/100, better than 51% 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 QT-HS 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 QT-HS?
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 QT-HS 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 QT-HS?
F6b QT-HS 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.
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. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.