Steel 50B60-SA (Spheroidize annealed)
Heat-treated state
EN 50B60 · UNS G50601
Choose for cold-headed fasteners or deep cold upsetting before hardening; lowest hardness and best cold ductility.
Values for the SA condition
Other 50B60 tempers and conditions
50B60 is listed in 10 conditions; see the grade overview at 50B60.
Compare all 10 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
SAThis page Spheroidize annealed | Choose for cold-headed fasteners or deep cold upsetting before hardening; lowest hardness and best cold ductility. | 400 | 690 | 22 | 11 HRC | 8.8 % IACS |
ADefault Solution annealed | Standard stock condition for bar that will be machined and then quenched and tempered by the user. | 420 | 750 | 16 | 217 HB | — |
Hot rolled | Lowest-cost mill condition for parts that will be fully heat treated after rough machining or forging. | 530 | 880 | 12 | 25 HRC | 8.6 % IACS |
Normalized | Used to homogenize forgings and refine grain before hardening; note that boron steels air-harden appreciably. | 620 | 1,000 | 11 | 30 HRC | 8.5 % IACS |
Cold drawn | Pick for close-tolerance, bright-surface bar going straight to machining; higher strength but residual stresses and reduced ductility. | 700 | 830 | 10 | 23 HRC | — |
Q&T | Softest quenched-and-tempered condition; used where machining after heat treatment and maximum ductility are needed. | 830 | 930 | 18 | 28 HRC | — |
Q&T | Tough through-hardened condition for shafts, links and machinery parts needing impact capability. | 1,050 | 1,160 | 14 | 36 HRC | — |
Q&T | Classic leaf-spring / torsion-bar condition balancing high elastic limit with usable toughness. | 1,350 | 1,450 | 11 | 44 HRC | — |
Q&T | High-hardness spring and wear condition; avoid 260–370 °C for impact-critical parts (temper embrittlement range). | 1,650 | 1,790 | 9 | 52 HRC | — |
Q&T | Maximum hardness and wear resistance for cutting edges and abrasion parts; very low toughness, brittle in impact. | 1,780 | 2,000 | 8 | 57 HRC | — |
What is 50B60-SA?
50B60-SA is 50B60 heat treated to SA — choose for cold-headed fasteners or deep cold upsetting before hardening; lowest hardness and best cold ductility. 50B60-SA has a yield strength of 400 MPa (58 ksi) and a tensile strength of 690 MPa (100 ksi) — weaker than 60% of steel grades. Elongation at break is 22% and the elastic modulus is 205 GPa (29.7 Msi). 50B60-SA 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). A is the default condition FabDigit quotes; SA is available on request or by drawing note.
Advantages
- Low embodied carbon — 1.9 kg CO₂/kg, better than 92% of steel grades
Limitations
- Low fracture toughness — 65 MPa·√m (59.2 ksi·√in), worse than 75% of steel grades
50B60-SA properties
Typical room-temperature values for 50B60-SA; 23 are specific to this condition. Other listed values are 50B60 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
50B60-SA 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).
Mechanical16
50B60-SA has a yield strength of 400 MPa (58 ksi) and a tensile strength of 690 MPa (100 ksi) — weaker than 60% of steel grades. Elongation at break is 22% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
50B60-SA is rated for continuous service to 400°C (752 °F). It conducts heat at 47 W/m·K (27.2 BTU/hr·ft·°F), better than 75% of steel grades. Thermal expansion is 12.3 µm/m·K (6.83 µin/in·°F).
Electrical3
50B60-SA 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 50B60-SA takes about 25 MJ of energy and emits 1.9 kg of CO₂ — less than 82% of steel grades. Typical recycled content is 30%.
Manufacturability7
50B60-SA's machinability is fair (48/100, worse than 57% of steel grades); weldability poor (30/100); formability good (55/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 50B60-SA
Is 50B60 easy to machine?
Machine in the annealed or spheroidized state (~60 % of 1212); use rigid setups, carbide tooling and moderate speeds — hardness above 40 HRC needs ceramic/CBN or grinding.
Can 50B60 be welded?
Poor weldability (CE ≈ 0.9): preheat 250–350 °C, low-hydrogen consumables, immediate post-weld temper; avoid welding on finished springs.
Can 50B60 be formed, bent or molded?
Hot form or forge at 1050–1200 °C; cold bending only after spheroidize annealing, otherwise expect cracking and heavy springback.
What surface finishes work on 50B60?
No natural corrosion resistance — shot peen springs for fatigue life, then phosphate + oil, zinc or Zn-Ni plate (bake 190 °C for hydrogen relief above 40 HRC) or paint.
50B60 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 | 0.56 – 0.64 | 0.6 |
| Mn | 0.75 – 1 | 0.88 |
| Si | 0.15 – 0.35 | 0.25 |
| Cr | 0.4 – 0.6 | 0.5 |
| Bhardenability booster; requires Ti/Al nitrogen fixing | 5×10⁻⁴ – 0 | 0 |
| P | ≤ 0.04 | — |
| S | ≤ 0.04 | — |
| Fe | balance | — |
50B60-SA — frequently asked
What is 50B60-SA used for?
50B60-SA is typically used for coil and leaf springs, high-strength bolts and clutch discs. In short: deep-hardening spring steel; higher carbon than 50B50; poor weldability by design.
What is the yield strength of 50B60-SA?
50B60-SA has a typical yield strength of 400 MPa (58 ksi) and a tensile strength of 690 MPa (100 ksi) — weaker than 60% of steel grades. Strength varies by condition: see the 10 listed tempers.
Is 50B60-SA easy to machine?
Reasonably — machinability is rated fair (48/100, worse than 57% of steel grades). Machine in the annealed or spheroidized state (~60 % of 1212); use rigid setups, carbide tooling and moderate speeds — hardness above 40 HRC needs ceramic/CBN or grinding.
Can 50B60-SA be welded?
Not readily — weldability is rated poor (30/100). Poor weldability (CE ≈ 0.9): preheat 250–350 °C, low-hydrogen consumables, immediate post-weld temper; avoid welding on finished springs.
What surface finishes work on 50B60-SA?
No natural corrosion resistance — shot peen springs for fatigue life, then phosphate + oil, zinc or Zn-Ni plate (bake 190 °C for hydrogen relief above 40 HRC) or paint.
Can 50B60-SA be formed, bent or molded?
Hot form or forge at 1050–1200 °C; cold bending only after spheroidize annealing, otherwise expect cracking and heavy springback.
What is the maximum service temperature of 50B60-SA?
50B60-SA is rated for continuous use to about 400°C (752 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 50B60-A and 50B60-QT205?
A is the default condition — standard stock condition for bar that will be machined and then quenched and tempered by the user. QT205: maximum hardness and wear resistance for cutting edges and abrasion parts; very low toughness, brittle in impact. Yield strength is 420 MPa in A versus 1,780 MPa in QT205.
Sources
- SAE J404 — Chemical Compositions of SAE Alloy Steels — SAE International (2021)
- SAE J1268 — Hardenability Bands for Boron H-Steels — SAE International (2018)
- ASTM A29/A29M — Steel Bars, Carbon and Alloy, Hot-Wrought — ASTM (2020)
- 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)
- Low-alloy boron steel property tables (typical Q&T curves) — FabDigit internal compilation (2025)
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.