Steel A229-CL2
Grade
ASTM A229 · JIS SWO-A/B, SWO-A
CL2 = class II
Pick when higher stress or smaller spring envelope is needed; ~10 % higher tensile than Class I at the cost of coilability.
Values for the CL2 condition
Other A229 tempers and conditions
A229 is listed in 3 conditions; see the grade overview at A229.
Compare all 3 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
CL1Default Class I | Default economy oil-tempered wire for static and lightly cycled springs; widest diameter availability and lowest price. | 1,320 | 1,550 | 7 | 45 HRC | — |
Class I, stress-relieved after coiling | Standard finished-spring condition: low-temperature bake after forming restores elastic limit, reduces set and relaxation. | 1,390 | 1,540 | 7 | 44 HRC | 9 % IACS |
CL2This page Class II | Pick when higher stress or smaller spring envelope is needed; ~10 % higher tensile than Class I at the cost of coilability. | 1,450 | 1,690 | 6 | 48 HRC | — |
What is A229-CL2?
A229-CL2 is A229 in the CL2 grade — pick when higher stress or smaller spring envelope is needed; ~10 % higher tensile than Class I at the cost of coilability. A229-CL2 has a yield strength of 1,450 MPa (210 ksi) and a tensile strength of 1,690 MPa (245 ksi) — stronger than 97% of steel grades. Elongation at break is 6% and the elastic modulus is 207 GPa (30 Msi). A229-CL2 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). CL1 is the default condition FabDigit quotes; CL2 is available on request or by drawing note.
Advantages
- High strength — 1,450 MPa (210 ksi), better than 97% of steel grades
Limitations
- Limited service temperature — 150°C (302 °F), worse than 99% of steel grades
- Limited ductility — 6%, worse than 97% of steel grades
- Low fracture toughness — 25 MPa·√m (22.8 ksi·√in), worse than 97% of steel grades
- Difficult to machine — 18/100, worse than 97% of steel grades
- Difficult to weld — 12/100, worse than 96% of steel grades
A229-CL2 properties
Typical room-temperature values for A229-CL2; 14 are specific to this condition. Other listed values are A229 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
A229-CL2 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).
Mechanical16
A229-CL2 has a yield strength of 1,450 MPa (210 ksi) and a tensile strength of 1,690 MPa (245 ksi) — stronger than 97% of steel grades. Elongation at break is 6% and the elastic modulus is 207 GPa (30 Msi).
Thermal6
A229-CL2 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
A229-CL2 conducts electricity at 9 % IACS, better than 71% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (10/100), worse than 86% of steel grades.
Sustainability4
Producing a kilogram of A229-CL2 takes about 29 MJ of energy and emits 2.2 kg of CO₂ — less than 53% of steel grades. Typical recycled content is 20%.
Manufacturability8
A229-CL2's machinability is poor (18/100, worse than 97% of steel grades); weldability not recommended (12/100); formability fair (35/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with A229-CL2
Is A229 easy to machine?
Supplied at 40–50 HRC, so cut with abrasive wheels or carbide/CBN and grind ends rather than turn or mill; annealing to machine destroys spring properties.
Can A229 be welded?
Effectively non-weldable for structural purposes — high carbon gives hard, crack-prone HAZ and local loss of temper; use mechanical hooks, loops or crimped ends instead.
Can A229 be formed, bent or molded?
Coil cold on standard spring machines (Class I coils easier than Class II), then stress relieve 230–290 °C for 20–30 min; keep bend radii generous and avoid sharp hook transitions.
What surface finishes work on A229?
Not anodizable; protect with oil, phosphate + oil, black oxide, zinc/mechanical galvanizing or powder coat — bake at ~200 °C after any acid pickling or electroplating to avoid hydrogen embrittlement; shot peening markedly improves fatigue life.
A229 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 |
|---|---|---|
| Cheat analysis range per ASTM A229; mill selects grade within range for the ordered tensile class | 0.55 – 0.85 | 0.68 |
| Mn | 0.3 – 1.2 | 0.75 |
| Si | 0.15 – 0.35 | 0.25 |
| P | ≤ 0.04 | — |
| S | ≤ 0.05 | — |
| Fe | balance | — |
A229-CL2 — frequently asked
What is A229-CL2 used for?
A229-CL2 is typically used for general coil springs, upholstery springs and mattress springs. In short: best cost-to-strength spring wire; oil-tempered, no post-hardening; weaker fatigue than music wire.
What is the yield strength of A229-CL2?
A229-CL2 has a typical yield strength of 1,450 MPa (210 ksi) and a tensile strength of 1,690 MPa (245 ksi) — stronger than 97% of steel grades. Strength varies by condition: see the 3 listed tempers.
Is A229-CL2 easy to machine?
Not especially — machinability is rated poor (18/100, worse than 97% of steel grades). Supplied at 40–50 HRC, so cut with abrasive wheels or carbide/CBN and grind ends rather than turn or mill; annealing to machine destroys spring properties.
Can A229-CL2 be welded?
Not readily — weldability is rated not recommended (12/100). Effectively non-weldable for structural purposes — high carbon gives hard, crack-prone HAZ and local loss of temper; use mechanical hooks, loops or crimped ends instead.
What surface finishes work on A229-CL2?
Not anodizable; protect with oil, phosphate + oil, black oxide, zinc/mechanical galvanizing or powder coat — bake at ~200 °C after any acid pickling or electroplating to avoid hydrogen embrittlement; shot peening markedly improves fatigue life.
Can A229-CL2 be formed, bent or molded?
Coil cold on standard spring machines (Class I coils easier than Class II), then stress relieve 230–290 °C for 20–30 min; keep bend radii generous and avoid sharp hook transitions.
What is the maximum service temperature of A229-CL2?
A229-CL2 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 A229-CL1 and A229-CL2?
CL1 is the default condition — default economy oil-tempered wire for static and lightly cycled springs; widest diameter availability and lowest price. CL2: pick when higher stress or smaller spring envelope is needed; ~10 % higher tensile than Class I at the cost of coilability. Yield strength is 1,320 MPa in CL1 versus 1,450 MPa in CL2.
Sources
- ASTM A229/A229M — Steel Wire, Quenched and Tempered for Mechanical Springs — ASTM International (2017)
- JIS G 3560 — Oil tempered carbon steel wire (SWO-A / SWO-B) — JSA (2018)
- Handbook of Spring Design — Spring Manufacturers Institute (SMI) (2013)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
- Oil-tempered spring wire product data — Suzuki Garphytten / Kiswire (typical mill data) (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.