Stainless Steel HN Aged
Heat-treated state
UNS J94213
Aged = aged / service-exposed
Reference condition for assessing repair or re-use of furnace parts after prolonged high-temperature service: strength rises slightly, room-temperature ductility and impact energy collapse.
Values for the Aged condition
Other HN tempers and conditions
HN is listed in 3 conditions; see the grade overview at HN.
Compare all 3 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
AS-CASTDefault no heat treatment, ASTM A297/A743 HN | Standard supply condition for HN furnace hardware; use for all high-temperature service where creep and carburization resistance matter. | 255 | 470 | 11 | 175 HB | — |
HN40 centrifugally cast tube | Choose for radiant tubes, reformer/carburizing furnace tubes: centrifugal casting gives a denser, finer columnar structure and slightly higher strength than static castings. | 275 | 500 | 10 | 185 HB | 1.7 % IACS |
AgedThis page Aged / service-exposed | Reference condition for assessing repair or re-use of furnace parts after prolonged high-temperature service: strength rises slightly, room-temperature ductility and impact energy collapse. | 310 | 490 | 4 | 200 HB | 1.8 % IACS |
What is HN Aged?
HN Aged is HN heat treated to Aged — reference condition for assessing repair or re-use of furnace parts after prolonged high-temperature service: strength rises slightly, room-temperature ductility and impact energy collapse. HN Aged has a yield strength of 310 MPa (45 ksi) and a tensile strength of 490 MPa (71.1 ksi) — weaker than 63% of stainless steel grades. Elongation at break is 4% and the elastic modulus is 182 GPa (26.4 Msi). HN Aged has a density of 7.83 g/cm³ (0.283 lb/in³), heavier than 58% of stainless steel grades. It melts at 1,315°C (2,399 °F). AS-CAST 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 — 4%, worse than 100% of stainless steel grades
- Limited formability — 2/100, worse than 100% of stainless steel grades
- Difficult to machine — 21/100, worse than 97% of stainless steel grades
- Hard to polish — 45/100, worse than 96% of stainless steel grades
- Difficult to weld — 22/100, worse than 94% of stainless steel grades
HN Aged properties
Typical room-temperature values for HN Aged; 22 are specific to this condition. Other listed values are HN reference data and may not represent this condition. Bars are the position among stainless steel grades.
Physical3
HN Aged has a density of 7.83 g/cm³ (0.283 lb/in³), heavier than 58% of stainless steel grades. It melts at 1,315°C (2,399 °F).
Mechanical14
HN Aged has a yield strength of 310 MPa (45 ksi) and a tensile strength of 490 MPa (71.1 ksi) — weaker than 63% of stainless steel grades. Elongation at break is 4% and the elastic modulus is 182 GPa (26.4 Msi).
Thermal6
HN Aged is rated for continuous service to 1,090°C (1,994 °F). It conducts heat at 13.5 W/m·K (7.8 BTU/hr·ft·°F), worse than 83% of stainless steel grades. Thermal expansion is 15.5 µm/m·K (8.61 µin/in·°F).
Electrical3
HN Aged conducts electricity at 1.8 % IACS, worse than 87% of stainless steel grades.
Chemical & Environmental3
Corrosion resistance is fair (50/100), worse than 78% of stainless steel grades.
Sustainability4
Producing a kilogram of HN Aged takes about 60 MJ of energy and emits 5 kg of CO₂ — more than 70% of stainless steel grades. Typical recycled content is 65%.
Manufacturability7
HN Aged's machinability is poor (21/100, worse than 97% of stainless steel grades); weldability poor (22/100); formability not recommended (2/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with HN Aged
Is HN easy to machine?
Machine with rigid setups, sharp carbide inserts, low speed / heavy positive feed and flood coolant; the massive carbide network and rapid work hardening make interrupted cuts and small drills the main failure modes — grind rather than turn hardened service-aged parts.
Can HN be welded?
Weldable by SMAW/GTAW/FCAW with matching HN or 25Cr-35Ni filler; preheat 150–250 °C, low heat input and slow cool to limit hot cracking, and expect drastically reduced ductility when welding parts already thermally aged (solution treat at ~1100 °C first if possible).
Can HN be formed, bent or molded?
Casting-only grade — sand, investment and centrifugal casting all practical; feed heavy sections generously, avoid abrupt section changes to control hot tearing, and design generous fillets since no cold forming or straightening is possible.
What surface finishes work on HN?
Normally supplied shot-blasted or pickled; a self-healing Cr₂O₃/spinel scale forms in service and needs no coating, but aluminizing or diffusion coatings can be applied for severe carburizing/sulphidizing duty.
HN 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 |
|---|---|---|
| CHN40 subgrade (A608) narrows to 0.35–0.45 | 0.2 – 0.5 | 0.35 |
| Cr | 19 – 23 | 21 |
| Ni | 23 – 27 | 25 |
| Mn | ≤ 2 | 1.2 |
| Simax; higher Si aids oxidation resistance | ≤ 2 | 1.4 |
| Moresidual, max | ≤ 0.5 | 0.1 |
| P | ≤ 0.04 | 0.02 |
| S | ≤ 0.04 | 0.02 |
| Fe | balance | — |
HN Aged — frequently asked
What is HN Aged used for?
HN Aged is typically used for carburizing furnace fixtures, radiant tubes and heat-treatment baskets. In short: best carburization resistance vs HK; good thermal-fatigue life; lower strength, higher nickel.
What is the yield strength of HN Aged?
HN Aged has a typical yield strength of 310 MPa (45 ksi) and a tensile strength of 490 MPa (71.1 ksi) — weaker than 63% of stainless steel grades. Strength varies by condition: see the 3 listed tempers.
Is HN Aged easy to machine?
Not especially — machinability is rated poor (21/100, worse than 97% of stainless steel grades). Machine with rigid setups, sharp carbide inserts, low speed / heavy positive feed and flood coolant; the massive carbide network and rapid work hardening make interrupted cuts and small drills the main failure modes — grind rather than turn hardened service-aged parts.
Can HN Aged be welded?
Not readily — weldability is rated poor (22/100). Weldable by SMAW/GTAW/FCAW with matching HN or 25Cr-35Ni filler; preheat 150–250 °C, low heat input and slow cool to limit hot cracking, and expect drastically reduced ductility when welding parts already thermally aged (solution treat at ~1100 °C first if possible).
What surface finishes work on HN Aged?
Normally supplied shot-blasted or pickled; a self-healing Cr₂O₃/spinel scale forms in service and needs no coating, but aluminizing or diffusion coatings can be applied for severe carburizing/sulphidizing duty.
Can HN Aged be formed, bent or molded?
Casting-only grade — sand, investment and centrifugal casting all practical; feed heavy sections generously, avoid abrupt section changes to control hot tearing, and design generous fillets since no cold forming or straightening is possible.
What is the maximum service temperature of HN Aged?
HN 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 HN AS-CAST and HN Aged?
AS-CAST is the default condition — standard supply condition for HN furnace hardware; use for all high-temperature service where creep and carburization resistance matter. Aged: reference condition for assessing repair or re-use of furnace parts after prolonged high-temperature service: strength rises slightly, room-temperature ductility and impact energy collapse. Yield strength is 255 MPa in AS-CAST versus 310 MPa in Aged.
Sources
- ASTM A297/A297M — Steel Castings, Iron-Chromium and Iron-Chromium-Nickel, Heat Resistant, for General Application — ASTM International (2019)
- ASTM A743/A743M — Castings, Iron-Chromium, Iron-Chromium-Nickel, Corrosion Resistant, for General Application — ASTM International (2019)
- ASTM A608/A608M — Centrifugally Cast Iron-Chromium-Nickel High-Alloy Tubing for Pressure Application at High Temperatures (grade HN40) — ASTM International (2018)
- Steel Castings Handbook, Supplement 9 — High Alloy Data Sheets, Heat Series — Steel Founders' Society of America (2004)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels, and High-Performance Alloys (heat-resistant castings) — ASM International (1990)
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.