Steel A897 Grade 3 AT+SP
Finish state
ASTM A897 Grade 3 · EN EN-GJS-1050-6 · GB QTA1050-6
AT+SP = austempered and shot peened
Shot peening after austempering induces strain-transformed martensite plus compressive residual stress; choose for gear roots and highly loaded fatigue parts.
Values for the AT+SP condition
Other A897 Grade 3 tempers and conditions
A897 Grade 3 is listed in 3 conditions; see the grade overview at A897 Grade 3.
Compare all 3 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Spheroidize annealed | Machining condition: alloyed ductile iron casting rough- and semi-finish machined in the soft state, then austempered to Grade 3 (allow ~0.05–0.1 % growth). | 400 | 620 | 10 | 16 HRC | 3.1 % IACS |
ATDefault Austempered to A897 Grade 3 | Standard as-supplied ADI Grade 3 condition: austenitized ~900 °C then salt-bath austempered ~315–345 °C; pick for gears, sprockets and wear parts needing 1050 MPa with usable ductility. | 810 | 1,120 | 8 | 36 HRC | — |
AT+SPThis page Austempered and shot peened | Shot peening after austempering induces strain-transformed martensite plus compressive residual stress; choose for gear roots and highly loaded fatigue parts. | 810 | 1,120 | 7 | 43 HRC | 2.7 % IACS |
What is A897 Grade 3 AT+SP?
A897 Grade 3 AT+SP is A897 Grade 3 supplied in the AT+SP condition — shot peening after austempering induces strain-transformed martensite plus compressive residual stress; choose for gear roots and highly loaded fatigue parts. A897 Grade 3 AT+SP has a yield strength of 810 MPa (117 ksi) and a tensile strength of 1,120 MPa (162 ksi) — stronger than 87% of steel grades. Elongation at break is 7% and the elastic modulus is 168 GPa (24.4 Msi). A897 Grade 3 AT+SP has a density of 7.1 g/cm³ (0.257 lb/in³), lighter than 99% of steel grades. It melts at 1,150°C (2,102 °F). AT is the default condition FabDigit quotes; AT+SP is available on request or by drawing note.
Advantages
- Good corrosion resistance — 22/100, better than 90% of steel grades
- High strength — 810 MPa (117 ksi), better than 87% of steel grades
Limitations
- Difficult to weld — 8/100, worse than 99% of steel grades
- Limited formability — 3/100, worse than 99% of steel grades
- Difficult to machine — 15/100, worse than 98% of steel grades
- Low stiffness — 168 GPa (24.4 Msi), worse than 97% of steel grades
- Limited ductility — 7%, worse than 96% of steel grades
A897 Grade 3 AT+SP properties
Typical room-temperature values for A897 Grade 3 AT+SP; 22 are specific to this condition. Other listed values are A897 Grade 3 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
A897 Grade 3 AT+SP has a density of 7.1 g/cm³ (0.257 lb/in³), lighter than 99% of steel grades. It melts at 1,150°C (2,102 °F).
Mechanical16
A897 Grade 3 AT+SP has a yield strength of 810 MPa (117 ksi) and a tensile strength of 1,120 MPa (162 ksi) — stronger than 87% of steel grades. Elongation at break is 7% and the elastic modulus is 168 GPa (24.4 Msi).
Thermal6
A897 Grade 3 AT+SP is rated for continuous service to 300°C (572 °F). It conducts heat at 22 W/m·K (12.7 BTU/hr·ft·°F), worse than 93% of steel grades. Thermal expansion is 13.5 µm/m·K (7.5 µin/in·°F).
Electrical3
A897 Grade 3 AT+SP conducts electricity at 2.7 % IACS, worse than 96% of steel grades.
Chemical & Environmental3
Corrosion resistance is poor (22/100), better than 90% of steel grades.
Sustainability4
Producing a kilogram of A897 Grade 3 AT+SP takes about 25 MJ of energy and emits 2 kg of CO₂ — less than 82% of steel grades. Typical recycled content is 80%.
Manufacturability8
A897 Grade 3 AT+SP's machinability is poor (15/100, worse than 98% of steel grades); weldability not recommended (8/100); formability not recommended (3/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with A897 Grade 3 AT+SP
Is A897 Grade 3 easy to machine?
Rough and finish machine in the as-cast/annealed state and allow for ~0.05–0.1 % growth during austempering; post-austempering cuts need CBN or ceramic inserts, rigid setups, low speed/high feed, and grinding for finish work.
Can A897 Grade 3 be welded?
Essentially not weldable in the austempered condition — heat destroys the ausferrite and forms martensite/carbides; if unavoidable, weld the ductile-iron blank with Ni electrodes before heat treatment.
Can A897 Grade 3 be formed, bent or molded?
Produced by green-sand or no-bake ductile-iron casting with tight nodularity (>85 %) and porosity control, then austenitized ~900 °C and salt-bath austempered ~315–345 °C for Grade 3 properties.
What surface finishes work on A897 Grade 3?
Not anodizable; protect with paint, e-coat, phosphate or oil. Shot peening greatly boosts fatigue life; avoid nitriding/plating processes exceeding ~300 °C.
A897 Grade 3 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 |
|---|---|---|
| Cchemistry not fixed by A897; foundry sets it to meet mechanical properties | 3 – 3.9 | 3.6 |
| Si | 2 – 3 | 2.5 |
| Mnkept low in heavy sections to avoid segregation | 0.15 – 0.5 | 0.3 |
| Cuhardenability addition | 0.2 – 0.9 | 0.6 |
| Nihardenability, heavier sections | 0 – 2 | 0.5 |
| Mohardenability; excess causes carbide segregation | 0 – 0.3 | 0.2 |
| Mgnodulizer, residual | 0.03 – 0.06 | 0.04 |
| P | ≤ 0.04 | 0.02 |
| S | ≤ 0.02 | 0.01 |
| Fe | balance | — |
A897 Grade 3 AT+SP — frequently asked
What is A897 Grade 3 AT+SP used for?
A897 Grade 3 AT+SP is typically used for heavy truck gears, differential housings and mining equipment parts. In short: steel strength at casting cost; strong-yet-ductile ADI grade; machine before austempering.
What is the yield strength of A897 Grade 3 AT+SP?
A897 Grade 3 AT+SP has a typical yield strength of 810 MPa (117 ksi) and a tensile strength of 1,120 MPa (162 ksi) — stronger than 87% of steel grades. Strength varies by condition: see the 3 listed tempers.
Is A897 Grade 3 AT+SP easy to machine?
Not especially — machinability is rated poor (15/100, worse than 98% of steel grades). Rough and finish machine in the as-cast/annealed state and allow for ~0.05–0.1 % growth during austempering; post-austempering cuts need CBN or ceramic inserts, rigid setups, low speed/high feed, and grinding for finish work.
Can A897 Grade 3 AT+SP be welded?
Not readily — weldability is rated not recommended (8/100). Essentially not weldable in the austempered condition — heat destroys the ausferrite and forms martensite/carbides; if unavoidable, weld the ductile-iron blank with Ni electrodes before heat treatment.
What surface finishes work on A897 Grade 3 AT+SP?
Not anodizable; protect with paint, e-coat, phosphate or oil. Shot peening greatly boosts fatigue life; avoid nitriding/plating processes exceeding ~300 °C.
Can A897 Grade 3 AT+SP be formed, bent or molded?
Produced by green-sand or no-bake ductile-iron casting with tight nodularity (>85 %) and porosity control, then austenitized ~900 °C and salt-bath austempered ~315–345 °C for Grade 3 properties.
What is the maximum service temperature of A897 Grade 3 AT+SP?
A897 Grade 3 AT+SP is rated for continuous use to about 300°C (572 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between A897 Grade 3-AT and A897 Grade 3-AC?
AT is the default condition — standard as-supplied ADI Grade 3 condition: austenitized ~900 °C then salt-bath austempered ~315–345 °C; pick for gears, sprockets and wear parts needing 1050 MPa with usable ductility. AC: machining condition: alloyed ductile iron casting rough- and semi-finish machined in the soft state, then austempered to Grade 3 (allow ~0.05–0.1 % growth). Yield strength is 810 MPa in AT versus 400 MPa in AC.
Sources
- ASTM A897/A897M — Standard Specification for Austempered Ductile Iron Castings — ASTM International (2016)
- EN 1564 — Founding: Ausferritic spheroidal graphite cast irons — CEN (2011)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
- Ductile Iron Data for Design Engineers (ADI section) — Ductile Iron Society / Rio Tinto Iron & Titanium (2013)
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.