Stainless Steel HF-AC (Spheroidize annealed)
Heat-treated state · default condition
UNS J92603
Standard supply condition for furnace and heat-treatment fixture castings that will operate hot; no post-cast heat treatment.
Values for the AC condition
Other HF tempers and conditions
HF is listed in 3 conditions; see the grade overview at HF.
Compare all 3 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Solution Annealed | Choose when the casting sees aqueous/corrosive service or needs maximum ductility and the most homogeneous carbide-free matrix. | 285 | 585 | 45 | 155 HB | 2.2 % IACS |
ACDefaultThis page Spheroidize annealed | Standard supply condition for furnace and heat-treatment fixture castings that will operate hot; no post-cast heat treatment. | 310 | 620 | 38 | 165 HB | — |
Aged / Service-Exposed | Use these numbers for design checks on parts that have already spent long periods in the 600–900 °C range — strength rises, toughness collapses. | 380 | 655 | 18 | 11 HRC | 2.4 % IACS |
What is HF-AC?
HF-AC is HF heat treated to AC — standard supply condition for furnace and heat-treatment fixture castings that will operate hot; no post-cast heat treatment. HF-AC has a yield strength of 310 MPa (45 ksi) and a tensile strength of 620 MPa (89.9 ksi) — weaker than 63% of stainless steel grades. Elongation at break is 38% and the elastic modulus is 193 GPa (28 Msi). HF-AC has a density of 7.75 g/cm³ (0.28 lb/in³), lighter than 65% of stainless steel grades. It melts at 1,400°C (2,552 °F).
Advantages
- High service temperature — 870°C (1,598 °F), better than 83% of stainless steel grades
Limitations
- Limited formability — 10/100, worse than 95% of stainless steel grades
- Hard to polish — 50/100, worse than 93% of stainless steel grades
- Difficult to weld — 50/100, worse than 77% of stainless steel grades
HF-AC properties
Typical room-temperature values for HF-AC; 11 are specific to this condition. Other listed values are HF reference data and may not represent this condition. Bars are the position among stainless steel grades.
Physical3
HF-AC has a density of 7.75 g/cm³ (0.28 lb/in³), lighter than 65% of stainless steel grades. It melts at 1,400°C (2,552 °F).
Mechanical13
HF-AC has a yield strength of 310 MPa (45 ksi) and a tensile strength of 620 MPa (89.9 ksi) — weaker than 63% of stainless steel grades. Elongation at break is 38% and the elastic modulus is 193 GPa (28 Msi).
Thermal6
HF-AC is rated for continuous service to 870°C (1,598 °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 17.3 µm/m·K (9.61 µin/in·°F).
Electrical3
HF-AC conducts electricity at 2.2 % IACS, worse than 61% of stainless steel grades.
Chemical & Environmental3
Corrosion resistance is good (55/100), worse than 71% of stainless steel grades.
Sustainability4
Producing a kilogram of HF-AC takes about 53 MJ of energy and emits 4.5 kg of CO₂ — less than 67% of stainless steel grades. Typical recycled content is 75%.
Manufacturability8
HF-AC's machinability is poor (30/100, worse than 70% of stainless steel grades); weldability fair (50/100); formability not recommended (10/100).
Common Calculations5
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with HF-AC
Is HF easy to machine?
Work-hardening and carbide-loaded — use rigid setups, positive-rake carbide (C2/K20 or coated grades), 30–60 m/min, heavy positive feed to stay under the hardened skin, and flood coolant.
Can HF be welded?
Weldable with ER308/E308 or over-alloyed ER312 for as-cast repair; preheat 150–200 °C on heavy sections, limit interpass, and re-solution-anneal if aqueous corrosion service follows.
Can HF be formed, bent or molded?
Sand or investment cast only; good fluidity but high solidification shrinkage (~2.2 %) demands generous risering and chills at section changes.
What surface finishes work on HF?
Grit blast plus pickle/passivate (ASTM A967) for corrosion service, or pre-oxidize at 900 °C to form a protective Cr₂O₃ scale before furnace duty; no anodizing.
HF 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 for creep strength; distinguishes HF from CF8 | 0.2 – 0.4 | 0.3 |
| Mn | ≤ 2 | 1.2 |
| Siaids fluidity and oxidation resistance | ≤ 2 | 1.3 |
| P | ≤ 0.04 | — |
| S | ≤ 0.04 | — |
| Cr | 19 – 23 | 21 |
| Ni | 9 – 12 | 10.5 |
| Moresidual only unless otherwise agreed | ≤ 0.5 | — |
| Fe | balance | — |
HF-AC — frequently asked
What is HF-AC used for?
HF-AC is typically used for furnace trays, grates and heat-treatment fixtures. In short: cast CF8 for heat service; ductile 18-8 heat-resistant grade; weldable furnace casting.
What is the yield strength of HF-AC?
HF-AC has a typical yield strength of 310 MPa (45 ksi) and a tensile strength of 620 MPa (89.9 ksi) — weaker than 63% of stainless steel grades. Strength varies by condition: see the 3 listed tempers.
Is HF-AC easy to machine?
Not especially — machinability is rated poor (30/100, worse than 70% of stainless steel grades). Work-hardening and carbide-loaded — use rigid setups, positive-rake carbide (C2/K20 or coated grades), 30–60 m/min, heavy positive feed to stay under the hardened skin, and flood coolant.
Can HF-AC be welded?
With care — weldability is rated fair (50/100). Weldable with ER308/E308 or over-alloyed ER312 for as-cast repair; preheat 150–200 °C on heavy sections, limit interpass, and re-solution-anneal if aqueous corrosion service follows.
What surface finishes work on HF-AC?
Grit blast plus pickle/passivate (ASTM A967) for corrosion service, or pre-oxidize at 900 °C to form a protective Cr₂O₃ scale before furnace duty; no anodizing.
Can HF-AC be formed, bent or molded?
Sand or investment cast only; good fluidity but high solidification shrinkage (~2.2 %) demands generous risering and chills at section changes.
What is the maximum service temperature of HF-AC?
HF-AC is rated for continuous use to about 870°C (1,598 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between HF-AC and HF Aged?
AC is the default condition — standard supply condition for furnace and heat-treatment fixture castings that will operate hot; no post-cast heat treatment. Aged: use these numbers for design checks on parts that have already spent long periods in the 600–900 °C range — strength rises, toughness collapses. Yield strength is 310 MPa in AC 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 A743/A743M — Castings, Iron-Chromium, Iron-Chromium-Nickel, Corrosion Resistant, for General Application — ASTM International (2019)
- 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)
- ASM Handbook Vol.13B — Corrosion: Materials — ASM International (2005)
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.