Stainless Steel HH Aged
Heat-treated state
UNS J93503
Aged = aged / service-exposed
Use these numbers when assessing residual room-temperature properties of parts that have run in the 650–900 °C range — strength rises but ductility and impact toughness collapse.
Values for the Aged condition
Other HH tempers and conditions
HH is listed in 7 conditions; see the grade overview at HH.
Compare all 7 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Solution annealed | Optional treatment to dissolve grain-boundary carbide networks before heavy machining or welding, giving better ductility at slightly lower strength. | 260 | 540 | 25 | 165 HB | 2 % IACS |
fully austenitic (ferrite-free) as-cast HH | Choose for continuous high-temperature service above ~900 °C where stable creep-rupture life and resistance to σ-embrittlement matter more than room-temperature strength. | 275 | 550 | 18 | 178 HB | 1.9 % IACS |
Centrifugally cast tube, 0.30 % C class | Centrifugally cast HH tubing for furnace radiant tubes and reformer-type service where creep-rupture strength is specified at temperature. | 300 | 570 | 14 | 185 HB | 2 % IACS |
FDefault As fabricated | Standard supply condition for HH furnace parts, radiant tubes and grate bars — used directly at temperature without heat treatment. | 310 | 585 | 15 | 185 HB | 2 % IACS |
Centrifugally cast tube, 0.33 % C class | Higher-carbon centrifugal HH tube grade for slightly greater creep-rupture strength at the cost of ductility and weldability. | 315 | 590 | 12 | 192 HB | 2 % IACS |
partially ferritic as-cast HH (A297/A447 Type I) | Choose when higher room- and intermediate-temperature strength is wanted and long holds in the 650–900 °C σ-phase range are avoided. | 345 | 600 | 12 | 192 HB | 2.1 % IACS |
AgedThis page Aged / service-exposed | Use these numbers when assessing residual room-temperature properties of parts that have run in the 650–900 °C range — strength rises but ductility and impact toughness collapse. | 380 | 620 | 5 | 17 HRC | 2.1 % IACS |
What is HH Aged?
HH Aged is HH heat treated to Aged — use these numbers when assessing residual room-temperature properties of parts that have run in the 650–900 °C range — strength rises but ductility and impact toughness collapse. HH Aged has a yield strength of 380 MPa (55.1 ksi) and a tensile strength of 620 MPa (89.9 ksi) — stronger than 52% of stainless steel grades. Elongation at break is 5% and the elastic modulus is 196 GPa (28.4 Msi). HH Aged has a density of 7.72 g/cm³ (0.279 lb/in³), lighter than 72% of stainless steel grades. It melts at 1,400°C (2,552 °F). F is the default condition FabDigit quotes; Aged is available on request or by drawing note.
Advantages
- High service temperature — 1,090°C (1,994 °F), better than 93% of stainless steel grades
Limitations
- Limited ductility — 5%, worse than 100% of stainless steel grades
- Limited formability — 2/100, worse than 100% of stainless steel grades
- Low fracture toughness — 25 MPa·√m (22.8 ksi·√in), worse than 99% of stainless steel grades
- Difficult to machine — 22/100, worse than 95% of stainless steel grades
- Difficult to weld — 25/100, worse than 92% of stainless steel grades
HH Aged properties
Typical room-temperature values for HH Aged; 23 are specific to this condition. Other listed values are HH reference data and may not represent this condition. Bars are the position among stainless steel grades.
Physical3
HH Aged has a density of 7.72 g/cm³ (0.279 lb/in³), lighter than 72% of stainless steel grades. It melts at 1,400°C (2,552 °F).
Mechanical15
HH Aged has a yield strength of 380 MPa (55.1 ksi) and a tensile strength of 620 MPa (89.9 ksi) — stronger than 52% of stainless steel grades. Elongation at break is 5% and the elastic modulus is 196 GPa (28.4 Msi).
Thermal6
HH Aged is rated for continuous service to 1,090°C (1,994 °F). It conducts heat at 15.5 W/m·K (8.96 BTU/hr·ft·°F), better than 53% of stainless steel grades. Thermal expansion is 15 µm/m·K (8.33 µin/in·°F).
Electrical3
HH Aged conducts electricity at 2.1 % IACS, worse than 73% of stainless steel grades.
Chemical & Environmental3
Corrosion resistance is fair (50/100), worse than 78% of stainless steel grades.
Sustainability4
Producing a kilogram of HH Aged takes about 48 MJ of energy and emits 4 kg of CO₂ — less than 85% of stainless steel grades. Typical recycled content is 75%.
Manufacturability7
HH Aged's machinability is poor (22/100, worse than 95% of stainless steel grades); weldability poor (25/100); formability not recommended (2/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with HH Aged
Is HH easy to machine?
Machine with rigid setups, positive-rake carbide and heavy feeds to cut under the work-hardened skin; the interdendritic carbide network is abrasive, so keep speeds low (~30–60 m/min) and flood-cool.
Can HH be welded?
Weldable with matching 25-12 (AWS ER309/E309) filler using low heat input and interpass control; preheat/postweld solution treatment reduces hot-cracking and carbide-network cracking in aged castings.
Can HH be formed, bent or molded?
Foundry grade only — sand or centrifugal cast with generous fillets and directional solidification; no cold forming, and hot straightening should be done above 1050 °C.
What surface finishes work on HH?
Shot-blast and pickle/passivate to remove casting scale; no anodizing — surfaces self-protect by forming a chromia scale in service, and machined faces can be ground/polished to a moderate finish.
HH 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 |
|---|---|---|
| Chigh carbon gives carbide strengthening | 0.2 – 0.5 | 0.35 |
| Cr | 24 – 28 | 26 |
| Ni | 11 – 14 | 12 |
| Siimproves fluidity and scaling resistance | ≤ 2 | 1.5 |
| Mn | ≤ 2 | 1 |
| Moresidual, not intentionally added | ≤ 0.5 | — |
| Npromotes austenite (Type II) | ≤ 0.2 | — |
| P | ≤ 0.04 | — |
| S | ≤ 0.04 | — |
| Fe | balance | — |
HH Aged — frequently asked
What is HH Aged used for?
HH Aged is typically used for furnace rollers, radiant tubes, heat-treatment baskets and kiln furniture. In short: baseline heat-resistant casting; oxidation resistance to 1090 °C; cast-only furnace alloy.
What is the yield strength of HH Aged?
HH Aged has a typical yield strength of 380 MPa (55.1 ksi) and a tensile strength of 620 MPa (89.9 ksi) — stronger than 52% of stainless steel grades. Strength varies by condition: see the 7 listed tempers.
Is HH Aged easy to machine?
Not especially — machinability is rated poor (22/100, worse than 95% of stainless steel grades). Machine with rigid setups, positive-rake carbide and heavy feeds to cut under the work-hardened skin; the interdendritic carbide network is abrasive, so keep speeds low (~30–60 m/min) and flood-cool.
Can HH Aged be welded?
Not readily — weldability is rated poor (25/100). Weldable with matching 25-12 (AWS ER309/E309) filler using low heat input and interpass control; preheat/postweld solution treatment reduces hot-cracking and carbide-network cracking in aged castings.
What surface finishes work on HH Aged?
Shot-blast and pickle/passivate to remove casting scale; no anodizing — surfaces self-protect by forming a chromia scale in service, and machined faces can be ground/polished to a moderate finish.
Can HH Aged be formed, bent or molded?
Foundry grade only — sand or centrifugal cast with generous fillets and directional solidification; no cold forming, and hot straightening should be done above 1050 °C.
What is the maximum service temperature of HH Aged?
HH Aged is rated for continuous use to about 1,090°C (1,994 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between HH-F and HH Aged?
F is the default condition — standard supply condition for HH furnace parts, radiant tubes and grate bars — used directly at temperature without heat treatment. Aged: use these numbers when assessing residual room-temperature properties of parts that have run in the 650–900 °C range — strength rises but ductility and impact toughness collapse. Yield strength is 310 MPa in F versus 380 MPa in Aged.
Sources
- ASTM A297/A297M — Steel Castings, Iron-Chromium and Iron-Chromium-Nickel, Heat Resistant, for General Application — ASTM International (2019)
- ASTM A447/A447M — Steel Castings, Chromium-Nickel-Iron Alloy (25-12 Class), for High-Temperature Service — ASTM International (2019)
- ASTM A608/A608M — Centrifugally Cast Iron-Chromium-Nickel High-Alloy Tubing for Pressure Application at High Temperatures — ASTM International (2018)
- ASM Specialty Handbook: Heat-Resistant Materials — ASM International (1997)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels, and High-Performance Alloys (Heat-Resistant Castings) — ASM International (1990)
- Steel Castings Handbook, 6th ed. — Steel Founders' Society of America / ASM (1995)
- GB/T 8492 — (ZG40Cr25Ni12) — SAC (2014)
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.