Steel A228-SR (Stress relieved)
Heat-treated state
ASTM A228 · UNS K08500 · JIS SWP-A/B
Standard post-coiling bake for springs: raises elastic limit, reduces set and hydrogen risk, tensile essentially unchanged.
Values for the SR condition
Other A228 tempers and conditions
A228 is listed in 6 conditions; see the grade overview at A228.
Compare all 6 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
as-drawn, diameter 3.0–6.5 mm | Larger diameters where tensile strength drops with size; upper size limit of A228 supply. | 1,650 | 1,950 | 4 | 47 HRC | 8.6 % IACS |
JIS G 3522 piano wire, class A | Japanese/Asian equivalent supply class at the lower of the two JIS strength bands; common in Chinese and Japanese spring shops. | 1,850 | 2,180 | 3.5 | 50 HRC | 8.5 % IACS |
CDDefault Cold drawn | Standard stocked condition: bright, oiled, as-drawn coil for general small spring coiling. | 1,950 | 2,300 | 3 | 52 HRC | 8.6 % IACS |
JIS G 3522 piano wire, class B | Higher JIS strength band, closest match to ASTM A228 tensile requirements for the same diameter. | 1,980 | 2,320 | 3 | 52 HRC | 8.5 % IACS |
SRThis page Stress relieved | Standard post-coiling bake for springs: raises elastic limit, reduces set and hydrogen risk, tensile essentially unchanged. | 2,050 | 2,320 | 3 | 52 HRC | 8.8 % IACS |
as-drawn, diameter ≤ 0.5 mm | Fine sizes reach the highest tensile levels of any carbon steel; used for micro springs and instrument strings. | 2,400 | 2,800 | 2 | 57 HRC | 8.3 % IACS |
What is A228-SR?
A228-SR is A228 heat treated to SR — standard post-coiling bake for springs: raises elastic limit, reduces set and hydrogen risk, tensile essentially unchanged. A228-SR has a yield strength of 2,050 MPa (297 ksi) and a tensile strength of 2,320 MPa (336 ksi) — stronger than 100% of steel grades. Elongation at break is 3% and the elastic modulus is 207 GPa (30 Msi). A228-SR has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,400°C (2,552 °F). CD is the default condition FabDigit quotes; SR is available on request or by drawing note.
Advantages
- High strength — 2,050 MPa (297 ksi), better than 100% of steel grades
Limitations
- Limited ductility — 3%, worse than 99% of steel grades
- Limited service temperature — 150°C (302 °F), worse than 99% of steel grades
- Difficult to weld — 10/100, worse than 99% of steel grades
- Difficult to machine — 16/100, worse than 98% of steel grades
A228-SR properties
Typical room-temperature values for A228-SR; 20 are specific to this condition. Other listed values are A228 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
A228-SR has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,400°C (2,552 °F).
Mechanical14
A228-SR has a yield strength of 2,050 MPa (297 ksi) and a tensile strength of 2,320 MPa (336 ksi) — stronger than 100% of steel grades. Elongation at break is 3% and the elastic modulus is 207 GPa (30 Msi).
Thermal6
A228-SR is rated for continuous service to 150°C (302 °F). It conducts heat at 46 W/m·K (26.6 BTU/hr·ft·°F), better than 71% of steel grades. Thermal expansion is 12.5 µm/m·K (6.94 µin/in·°F).
Electrical3
A228-SR conducts electricity at 8.8 % IACS, better than 69% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (10/100), worse than 86% of steel grades.
Sustainability4
Producing a kilogram of A228-SR takes about 27 MJ of energy and emits 2.1 kg of CO₂ — less than 59% of steel grades. Typical recycled content is 25%.
Manufacturability6
A228-SR's machinability is poor (16/100, worse than 98% of steel grades); weldability not recommended (10/100); formability poor (25/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with A228-SR
Is A228 easy to machine?
Essentially not machined — grind or abrasive/EDM cut; wire is cut to length with shear or abrasive wheel, and cold-drawn hardness wrecks HSS tooling.
Can A228 be welded?
Do not weld the working part: any fusion or resistance weld anneals the drawn pearlite and creates a brittle low-strength zone; use mechanical hooks/loops or crimped terminals.
Can A228 be formed, bent or molded?
Coil cold on CNC spring machines with generous mandrel ratio (D/d ≥ 4), then stress relieve 200–260 °C for 20–30 min; sharp bends and tight hook radii cause longitudinal splitting.
What surface finishes work on A228?
Ship oiled; for corrosion use phosphate+oil, tin or zinc coating, or mechanical galvanizing — after acid pickling or electroplating bake 190–230 °C for 4 h to avoid hydrogen embrittlement; shot peening markedly raises fatigue life.
A228 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 |
|---|---|---|
| Ccarbon level selected by diameter/strength class | 0.7 – 1 | 0.85 |
| Mn | 0.2 – 0.6 | 0.4 |
| Si | 0.1 – 0.3 | 0.2 |
| P | ≤ 0.03 | 0.01 |
| S | ≤ 0.03 | 0.01 |
| Fe | balance | — |
A228-SR — frequently asked
What is A228-SR used for?
A228-SR is typically used for precision small coil springs, musical instrument strings, clock springs and wire forms. In short: highest-strength carbon spring wire; best fatigue uniformity; low service temperature limit.
What is the yield strength of A228-SR?
A228-SR has a typical yield strength of 2,050 MPa (297 ksi) and a tensile strength of 2,320 MPa (336 ksi) — stronger than 100% of steel grades. Strength varies by condition: see the 6 listed tempers.
Is A228-SR easy to machine?
Not especially — machinability is rated poor (16/100, worse than 98% of steel grades). Essentially not machined — grind or abrasive/EDM cut; wire is cut to length with shear or abrasive wheel, and cold-drawn hardness wrecks HSS tooling.
Can A228-SR be welded?
Not readily — weldability is rated not recommended (10/100). Do not weld the working part: any fusion or resistance weld anneals the drawn pearlite and creates a brittle low-strength zone; use mechanical hooks/loops or crimped terminals.
What surface finishes work on A228-SR?
Ship oiled; for corrosion use phosphate+oil, tin or zinc coating, or mechanical galvanizing — after acid pickling or electroplating bake 190–230 °C for 4 h to avoid hydrogen embrittlement; shot peening markedly raises fatigue life.
Can A228-SR be formed, bent or molded?
Coil cold on CNC spring machines with generous mandrel ratio (D/d ≥ 4), then stress relieve 200–260 °C for 20–30 min; sharp bends and tight hook radii cause longitudinal splitting.
What is the maximum service temperature of A228-SR?
A228-SR is rated for continuous use to about 150°C (302 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between A228-CD and A228 CD-FINE?
CD is the default condition — standard stocked condition: bright, oiled, as-drawn coil for general small spring coiling. CD-FINE: fine sizes reach the highest tensile levels of any carbon steel; used for micro springs and instrument strings. Yield strength is 1,950 MPa in CD versus 2,400 MPa in CD-FINE.
Sources
- ASTM A228/A228M — Standard Specification for Steel Wire, Music Spring Quality — ASTM International (2021)
- JIS G 3522 — Piano wire (SWP-A/SWP-B) — JSA (2014)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels, and High-Performance Alloys (Spring Steels) — ASM International (1990)
- Design Handbook: Engineering Guide to Spring Design — Associated Spring / Barnes Group (1987)
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.