Steel A227-SR (Stress relieved)
Heat-treated state
ASTM A227
Standard post-coiling low-temperature bake that restores elastic limit, reduces set/relaxation and removes plating hydrogen; use for all finished springs.
Values for the SR condition
Other A227 tempers and conditions
A227 is listed in 3 conditions; see the grade overview at A227.
Compare all 3 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
CLIDefault Class I | Default general-purpose hard-drawn spring wire for moderate-stress static or low-cycle springs where cost matters. | 1,380 | 1,620 | 4 | 46 HRC | — |
SRThis page Stress relieved | Standard post-coiling low-temperature bake that restores elastic limit, reduces set/relaxation and removes plating hydrogen; use for all finished springs. | 1,480 | 1,650 | 4 | 47 HRC | 9.5 % IACS |
Class II | Choose when a higher stress level or smaller spring index is required; tensile is roughly 10 % above Class I at the same diameter, with slightly less ductility for coiling. | 1,520 | 1,790 | 3 | 49 HRC | — |
What is A227-SR?
A227-SR is A227 heat treated to SR — standard post-coiling low-temperature bake that restores elastic limit, reduces set/relaxation and removes plating hydrogen; use for all finished springs. A227-SR has a yield strength of 1,480 MPa (215 ksi) and a tensile strength of 1,650 MPa (239 ksi) — stronger than 97% of steel grades. Elongation at break is 4% and the elastic modulus is 207 GPa (30 Msi). A227-SR has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,425°C (2,597 °F). CLI is the default condition FabDigit quotes; SR is available on request or by drawing note.
Advantages
- High strength — 1,480 MPa (215 ksi), better than 97% of steel grades
- Conducts heat well — 48 W/m·K (27.7 BTU/hr·ft·°F), better than 79% of steel grades
- High electrical conductivity — 9.5 % IACS, better than 75% of steel grades
Limitations
- Limited service temperature — 120°C (248 °F), worse than 100% of steel grades
- Limited ductility — 4%, worse than 98% of steel grades
- Difficult to machine — 22/100, worse than 95% of steel grades
- Low fracture toughness — 38 MPa·√m (34.6 ksi·√in), worse than 93% of steel grades
- Difficult to weld — 15/100, worse than 91% of steel grades
A227-SR properties
Typical room-temperature values for A227-SR; 22 are specific to this condition. Other listed values are A227 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
A227-SR has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,425°C (2,597 °F).
Mechanical15
A227-SR has a yield strength of 1,480 MPa (215 ksi) and a tensile strength of 1,650 MPa (239 ksi) — stronger than 97% of steel grades. Elongation at break is 4% and the elastic modulus is 207 GPa (30 Msi).
Thermal6
A227-SR is rated for continuous service to 120°C (248 °F). It conducts heat at 48 W/m·K (27.7 BTU/hr·ft·°F), better than 79% of steel grades. Thermal expansion is 12.2 µm/m·K (6.78 µin/in·°F).
Electrical3
A227-SR conducts electricity at 9.5 % IACS, better than 75% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (10/100), worse than 86% of steel grades.
Sustainability4
Producing a kilogram of A227-SR takes about 28 MJ of energy and emits 2.1 kg of CO₂ — less than 56% of steel grades. Typical recycled content is 25%.
Manufacturability7
A227-SR's machinability is poor (22/100, worse than 95% of steel grades); weldability poor (15/100); formability fair (40/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with A227-SR
Is A227 easy to machine?
Rarely machined — the drawn wire is hard and abrasive; grind, shear, or abrasive-cut ends rather than turn or drill.
Can A227 be welded?
Essentially unweldable in service condition: 0.45–0.85 % C gives a brittle martensitic HAZ; use mechanical hooks/loops or resistance-weld only with a controlled post-weld temper.
Can A227 be formed, bent or molded?
Cold-coiled on CNC spring formers straight from the spool; keep spring index ≥4, then bake 230–290 °C for 20–30 min to relieve coiling stresses and set the free length.
What surface finishes work on A227?
Ship oiled or phosphated for indoor use; for corrosion service use mechanical zinc, hot-dip galvanize, or Zn-Ni plate with a post-plate hydrogen-relief bake at 190–220 °C within 4 h.
A227 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 |
|---|---|---|
| CASTM A227 heat analysis; the Chinese equivalent 65Mn sits at 0.62–0.70 % C | 0.45 – 0.85 | 0.65 |
| Mn65Mn: 0.90–1.20 % | 0.3 – 1.3 | 0.8 |
| P | ≤ 0.04 | 0.02 |
| S | ≤ 0.05 | 0.03 |
| Sitypical for 65Mn / silicon-killed rod; not always specified in A227 | 0.15 – 0.35 | 0.25 |
| Fe | balance | — |
A227-SR — frequently asked
What is A227-SR used for?
A227-SR is typically used for mechanical springs, clips, wire forms and general-purpose coil springs. In short: cheapest general spring wire; cold-coiled as drawn; not fatigue-rated.
What is the yield strength of A227-SR?
A227-SR has a typical yield strength of 1,480 MPa (215 ksi) and a tensile strength of 1,650 MPa (239 ksi) — stronger than 97% of steel grades. Strength varies by condition: see the 3 listed tempers.
Is A227-SR easy to machine?
Not especially — machinability is rated poor (22/100, worse than 95% of steel grades). Rarely machined — the drawn wire is hard and abrasive; grind, shear, or abrasive-cut ends rather than turn or drill.
Can A227-SR be welded?
Not readily — weldability is rated poor (15/100). Essentially unweldable in service condition: 0.45–0.85 % C gives a brittle martensitic HAZ; use mechanical hooks/loops or resistance-weld only with a controlled post-weld temper.
What surface finishes work on A227-SR?
Ship oiled or phosphated for indoor use; for corrosion service use mechanical zinc, hot-dip galvanize, or Zn-Ni plate with a post-plate hydrogen-relief bake at 190–220 °C within 4 h.
Can A227-SR be formed, bent or molded?
Cold-coiled on CNC spring formers straight from the spool; keep spring index ≥4, then bake 230–290 °C for 20–30 min to relieve coiling stresses and set the free length.
What is the maximum service temperature of A227-SR?
A227-SR is rated for continuous use to about 120°C (248 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between A227-CLI and A227 CLII?
CLI is the default condition — default general-purpose hard-drawn spring wire for moderate-stress static or low-cycle springs where cost matters. CLII: choose when a higher stress level or smaller spring index is required; tensile is roughly 10 % above Class I at the same diameter, with slightly less ductility for coiling. Yield strength is 1,380 MPa in CLI versus 1,520 MPa in CLII.
Sources
- ASTM A227/A227M — Standard Specification for Steel Wire, Cold-Drawn for Mechanical Springs — ASTM International (2017)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels, and High-Performance Alloys (Spring Steels) — ASM International (1990)
- Handbook of Spring Design — Spring Manufacturers Institute (SMI) (2013)
- ASTM A370 — Mechanical Testing of Steel Products (hardness conversions) — ASTM International (2022)
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.