Stainless Steel HH
UNS J93503
HH is a chromium-nickel heat-resistant cast stainless steel (UNS J93503) covered by ASTM A297, A351 and A743, available as Type I (partially ferritic) or Type II (fully austenitic) and in the HH30 and HH33 carbon grades.
Reference datasheet — HH 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 F condition
HH tempers and conditions
HH is supplied in 7 conditions, soft to hard. F is the default FabDigit quotes; the values on this page are for it.
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 |
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?
HH is a chromium-nickel heat-resistant cast stainless steel (UNS J93503) covered by ASTM A297, A351 and A743, available as Type I (partially ferritic) or Type II (fully austenitic) and in the HH30 and HH33 carbon grades. Engineers specify it for oxidation resistance and creep strength in furnace hardware to about 1090 °C, with 310 MPa yield, 585 MPa tensile, 15% elongation and 185 HB in the default condition. It is a foundry alloy only — sand, investment or centrifugal castings, no cold forming — and long exposure can embrittle the structure through sigma phase and carbide networks. Where higher temperature capability is needed, HK is the usual step up. HH 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). HH has a yield strength of 310 MPa (45 ksi) and a tensile strength of 585 MPa (84.8 ksi) — weaker than 63% of stainless steel grades. Elongation at break is 15% and the elastic modulus is 190 GPa (27.6 Msi).
What is HH used for?
- furnace rollers
- radiant tubes
- heat-treatment baskets
- kiln furniture
Advantages
- High service temperature — 1,090°C (1,994 °F), better than 93% of stainless steel grades
Limitations
- Limited formability — 8/100, worse than 97% of stainless steel grades
- Limited ductility — 15%, worse than 89% of stainless steel grades
- Hard to polish — 55/100, worse than 89% of stainless steel grades
- Low fracture toughness — 70 MPa·√m (63.7 ksi·√in), worse than 83% of stainless steel grades
- Difficult to weld — 45/100, worse than 79% of stainless steel grades
HH properties
Typical room-temperature values for HH-F; bars are the position among stainless steel grades.
Physical3
HH 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 has a yield strength of 310 MPa (45 ksi) and a tensile strength of 585 MPa (84.8 ksi) — weaker than 63% of stainless steel grades. Elongation at break is 15% and the elastic modulus is 190 GPa (27.6 Msi).
Thermal6
HH is rated for continuous service to 1,090°C (1,994 °F). It conducts heat at 14.2 W/m·K (8.2 BTU/hr·ft·°F), worse than 76% of stainless steel grades. Thermal expansion is 15 µm/m·K (8.33 µin/in·°F).
Electrical3
HH conducts electricity at 2 % IACS, worse than 77% of stainless steel grades.
Chemical & Environmental3
Corrosion resistance is good (62/100), worse than 52% of stainless steel grades.
Sustainability4
Producing a kilogram of HH 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's machinability is poor (30/100, worse than 70% of stainless steel grades); weldability fair (45/100); formability not recommended (8/100).
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. HH is highlighted; hover a dot for its name, or open the interactive family chart.
Working with HH
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.
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 |
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.
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 HH in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- UNS
- J93503
How much does HH cost?
HH 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.
HH — frequently asked
What is HH used for?
HH 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?
HH has a typical yield strength of 310 MPa (45 ksi) and a tensile strength of 585 MPa (84.8 ksi) — weaker than 63% of stainless steel grades. Strength varies by condition: see the 7 listed tempers.
Is HH easy to machine?
Not especially — machinability is rated poor (30/100, worse than 70% 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 be welded?
With care — weldability is rated fair (45/100). 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?
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 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?
HH 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.
How much does HH cost?
HH 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 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; 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.