Steel A232-SP (Shot peened)
Finish state
ASTM A232
Add shot peening after quench-and-temper or stress relief on high-cycle fatigue springs; compressive surface stress raises the fatigue limit while hardness stays at 50 HRC.
Values for the SP condition
Other A232 tempers and conditions
A232 is listed in 10 conditions; see the grade overview at A232.
Compare all 10 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Solution annealed | Choose for machining, blanking or deep forming before final quench and temper; the spheroidized structure gives 200 HB and 22% elongation but a low elastic limit. | 415 | 670 | 22 | 200 HB | — |
Normalized | Use as the intermediate state for forgings and hot-rolled flats needing a uniform structure at 940 MPa tensile, ready for subsequent quenching and tempering. | 615 | 940 | 22 | 27 HRC | 7.8 % IACS |
Cold drawn | Pick for low-cost cold-coiled springs or blanks to be hardened later; as-drawn 980 MPa yield with 8% elongation, but elastic limit below oil-tempered material. | 980 | 1,150 | 8 | 36 HRC | 7.5 % IACS |
oil quenched, tempered ~540 °C | Choose when toughness leads — torsion bars, heavy leaf springs and high-impact parts — accepting 1160 MPa yield after oil quenching and tempering near 540 °C. | 1,160 | 1,275 | 13 | 38 HRC | — |
oil quenched, tempered ~425 °C | Pick this common leaf- and flat-spring hardness band for balanced strength and toughness: oil quenched and tempered near 425 °C for 1410 MPa yield, 44 HRC, 300 °C service. | 1,410 | 1,550 | 10 | 44 HRC | — |
OTDefault Oil tempered | Pick the as-supplied oil-quenched and tempered wire or strip for springs cold coiled directly and then only stress relieved; 1750 MPa tensile at 50 HRC limits forming and welding. | 1,550 | 1,750 | 8 | 50 HRC | — |
SPThis page Shot peened | Add shot peening after quench-and-temper or stress relief on high-cycle fatigue springs; compressive surface stress raises the fatigue limit while hardness stays at 50 HRC. | 1,570 | 1,780 | 8 | 50 HRC | 7.5 % IACS |
Stress relieved | Apply as the standard final treatment on springs formed from oil-tempered stock: a 250–400 °C relief restores the 1620 MPa elastic limit and stabilizes dimensions. | 1,620 | 1,780 | 7 | 50 HRC | 7.5 % IACS |
Q&T 53–56 HRC | Select for wear-resistant, small-section parts needing 55 HRC after a 205 °C temper; brittleness limits it to low-impact duty up to 180 °C. | 1,690 | 1,930 | 8 | 55 HRC | — |
oil quenched, tempered ~315 °C | Use for high-stress valve springs, flat springs and retaining rings where the 1720 MPa elastic limit from a 315 °C temper outweighs the loss of toughness. | 1,720 | 1,860 | 8 | 50 HRC | — |
What is A232-SP?
A232-SP is A232 supplied in the SP condition — add shot peening after quench-and-temper or stress relief on high-cycle fatigue springs; compressive surface stress raises the fatigue limit while hardness stays at 50 HRC. A232-SP has a yield strength of 1,570 MPa (228 ksi) and a tensile strength of 1,780 MPa (258 ksi) — stronger than 98% of steel grades. Elongation at break is 8% and the elastic modulus is 207 GPa (30 Msi). A232-SP has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,420°C (2,588 °F). OT is the default condition FabDigit quotes; SP is available on request or by drawing note.
Advantages
- High strength — 1,570 MPa (228 ksi), better than 98% of steel grades
- Polishes to a fine finish — 65/100, better than 78% of steel grades
Limitations
- Difficult to machine — 18/100, worse than 97% of steel grades
- Limited ductility — 8%, worse than 95% of steel grades
- Difficult to weld — 15/100, worse than 91% of steel grades
- Low fracture toughness — 45 MPa·√m (41 ksi·√in), worse than 90% of steel grades
- Limited service temperature — 230°C (446 °F), worse than 88% of steel grades
A232-SP properties
Typical room-temperature values for A232-SP; 22 are specific to this condition. Other listed values are A232 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
A232-SP has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,420°C (2,588 °F).
Mechanical15
A232-SP has a yield strength of 1,570 MPa (228 ksi) and a tensile strength of 1,780 MPa (258 ksi) — stronger than 98% of steel grades. Elongation at break is 8% and the elastic modulus is 207 GPa (30 Msi).
Thermal6
A232-SP is rated for continuous service to 230°C (446 °F). It conducts heat at 46 W/m·K (26.6 BTU/hr·ft·°F), better than 71% of steel grades. Thermal expansion is 12.2 µm/m·K (6.78 µin/in·°F).
Electrical3
A232-SP conducts electricity at 7.5 % IACS, worse than 67% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (14/100), better than 70% of steel grades.
Sustainability4
Producing a kilogram of A232-SP takes about 31 MJ of energy and emits 2.3 kg of CO₂ — more than 64% of steel grades. Typical recycled content is 25%.
Manufacturability6
A232-SP's machinability is poor (18/100, worse than 97% of steel grades); weldability poor (15/100); formability poor (20/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with A232-SP
Is A232 easy to machine?
Turns and mills normally in the annealed condition at about 60 % of AISI 1212. Once quenched and tempered to 45 HRC or higher, work is effectively limited to grinding or finish turning with CBN tooling.
Can A232 be welded?
Carbon equivalent is high and the hardening tendency strong, so welding of finished springs is not recommended. Where welding is unavoidable, preheat 150–300 °C and temper immediately; fatigue performance drops significantly after welding.
Can A232 be formed, bent or molded?
Oil-tempered stock can only be cold coiled or cold bent with a bend radius of 3–4 t or more; complex shapes should be formed in the annealed or heated condition and then quenched and tempered. Stress relieve at 250–400 °C after forming.
What surface finishes work on A232?
Common systems are phosphate plus oil, shot peening followed by epoxy powder, or Dacromet coating. After zinc or cadmium plating, bake at 190–220 °C for at least 4 h to prevent hydrogen embrittlement.
A232 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 |
|---|---|---|
| C | 0.48 – 0.53 | 0.5 |
| Mn | 0.6 – 0.9 | 0.75 |
| Si | 0.15 – 0.35 | 0.25 |
| Cr | 0.8 – 1.1 | 0.95 |
| V0.15% min; refines grain and raises temper resistance | ≥ 0.15 | 0.18 |
| P | ≤ 0.04 | — |
| Smaximum; valve spring grades often held lower | ≤ 0.04 | — |
| Fe | balance | — |
A232-SP — frequently asked
What is A232-SP used for?
A232-SP is typically used for leaf springs, flat springs and clamps. In short: flat-form Cr-V spring steel; tempers to 55 HRC; poor weldability, coat for service.
What is the yield strength of A232-SP?
A232-SP has a typical yield strength of 1,570 MPa (228 ksi) and a tensile strength of 1,780 MPa (258 ksi) — stronger than 98% of steel grades. Strength varies by condition: see the 10 listed tempers.
Is A232-SP easy to machine?
Not especially — machinability is rated poor (18/100, worse than 97% of steel grades). Turns and mills normally in the annealed condition at about 60 % of AISI 1212. Once quenched and tempered to 45 HRC or higher, work is effectively limited to grinding or finish turning with CBN tooling.
Can A232-SP be welded?
Not readily — weldability is rated poor (15/100). Carbon equivalent is high and the hardening tendency strong, so welding of finished springs is not recommended. Where welding is unavoidable, preheat 150–300 °C and temper immediately; fatigue performance drops significantly after welding.
What surface finishes work on A232-SP?
Common systems are phosphate plus oil, shot peening followed by epoxy powder, or Dacromet coating. After zinc or cadmium plating, bake at 190–220 °C for at least 4 h to prevent hydrogen embrittlement.
Can A232-SP be formed, bent or molded?
Oil-tempered stock can only be cold coiled or cold bent with a bend radius of 3–4 t or more; complex shapes should be formed in the annealed or heated condition and then quenched and tempered. Stress relieve at 250–400 °C after forming.
What is the maximum service temperature of A232-SP?
A232-SP is rated for continuous use to about 230°C (446 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between A232-OT and A232-A?
OT is the default condition — pick the as-supplied oil-quenched and tempered wire or strip for springs cold coiled directly and then only stress relieved; 1750 MPa tensile at 50 HRC limits forming and welding. A: choose for machining, blanking or deep forming before final quench and temper; the spheroidized structure gives 200 HB and 22% elongation but a low elastic limit. Yield strength is 1,550 MPa in OT versus 415 MPa in A.
Sources
- ASTM A232/A232M — Chromium-Vanadium Alloy Steel Valve Spring Quality Wire — ASTM International (2020)
- SAE J404 / AISI 6150 alloy steel composition — SAE International (2019)
- GB/T 1222 50CrVA (2016)
- ASM Handbook Vol.1: Properties and Selection — Irons, Steels, and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol.4: Heat Treating — ASM International (1991)
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.