Steel C50-AC (Spheroidize annealed)
Heat-treated state
EN C50 · AISI/SAE 1050 · JIS S50C · GB 50
Choose when maximum cold-formability (upsetting, cold heading, deep machining) is needed before hardening.
Values for the AC condition
Other C50 tempers and conditions
C50 is listed in 11 conditions; see the grade overview at C50.
Compare all 11 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
ACThis page Spheroidize annealed | Choose when maximum cold-formability (upsetting, cold heading, deep machining) is needed before hardening. | 350 | 600 | 26 | 175 HB | 11 % IACS |
Solution annealed | Softest condition — pick for heavy machining, deep cold forming or before further heat treatment. | 365 | 636 | 24 | 187 HB | 50 W/m·K |
Hot rolled | Cheapest mill condition for stock removal parts that will be heat treated afterwards. | 415 | 725 | 15 | 197 HB | — |
NDefault Normalized | Standard stocked/uniform-structure condition: balanced strength and machinability, good base for later Q&T or induction hardening. | 425 | 750 | 20 | 217 HB | — |
Induction hardened | Use for shafts, gear teeth and rails needing a hard wear surface (55–62 HRC) with a tough unhardened core. | 500 | 800 | 15 | 58 HRC | 9.5 % IACS |
Cold drawn / cold finished bar | Pick for close tolerance, bright surface shafting where higher yield strength and short chips matter more than ductility. | 580 | 720 | 10 | 207 HB | — |
Quenched and tempered | Standard supply-condition Q&T for small sections needing guaranteed minimum yield with usable toughness. | 580 | 870 | 15 | 26 HRC | — |
Q&T 28–32 HRC (temper ~580–620 °C) | Tough general-purpose shaft/gear-blank condition; still readily machinable after heat treat. | 760 | 960 | 16 | 30 HRC | — |
Q&T 34–38 HRC (temper ~500–540 °C) | Higher-strength Q&T for moderately loaded gears, couplings and spindles where some toughness is still needed. | 950 | 1,150 | 12 | 36 HRC | — |
Q&T 40–45 HRC (temper ~400–450 °C) | Wear-oriented Q&T for small sections — high strength, limited ductility and low impact energy. | 1,150 | 1,350 | 9 | 43 HRC | — |
Hardened + low temper 150–200 °C | Maximum hardness/wear resistance for thin sections, springs and tools; brittle, avoid impact and stress raisers. | 1,600 | 1,900 | 3 | 56 HRC | — |
What is C50-AC?
C50-AC is C50 heat treated to AC — choose when maximum cold-formability (upsetting, cold heading, deep machining) is needed before hardening. C50-AC has a yield strength of 350 MPa (50.8 ksi) and a tensile strength of 600 MPa (87 ksi) — weaker than 74% of steel grades. Elongation at break is 26% and the elastic modulus is 210 GPa (30.5 Msi). C50-AC 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). N is the default condition FabDigit quotes; AC is available on request or by drawing note.
Advantages
- High electrical conductivity — 11 % IACS, better than 98% of steel grades
- Low embodied carbon — 1.9 kg CO₂/kg, better than 92% of steel grades
- Easy to machine — 62/100, better than 89% of steel grades
- Conducts heat well — 50 W/m·K (28.9 BTU/hr·ft·°F), better than 87% of steel grades
- Ductile — tolerates forming and impact — 26%, better than 82% of steel grades
C50-AC properties
Typical room-temperature values for C50-AC; 22 are specific to this condition. Other listed values are C50 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
C50-AC 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
C50-AC has a yield strength of 350 MPa (50.8 ksi) and a tensile strength of 600 MPa (87 ksi) — weaker than 74% of steel grades. Elongation at break is 26% and the elastic modulus is 210 GPa (30.5 Msi).
Thermal6
C50-AC is rated for continuous service to 350°C (662 °F). It conducts heat at 50 W/m·K (28.9 BTU/hr·ft·°F), better than 87% of steel grades. Thermal expansion is 11.5 µm/m·K (6.39 µin/in·°F).
Electrical3
C50-AC conducts electricity at 11 % IACS, better than 98% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (10/100), worse than 86% of steel grades.
Sustainability4
Producing a kilogram of C50-AC takes about 25 MJ of energy and emits 1.9 kg of CO₂ — less than 82% of steel grades. Typical recycled content is 30%.
Manufacturability6
C50-AC's machinability is good (62/100, better than 89% of steel grades); weldability fair (36/100); formability fair (46/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with C50-AC
Is C50 easy to machine?
Machines best at 180–220 HB (annealed/normalized); above 32 HRC use coated carbide, rigid setups and reduced feeds — no free-machining sulfur unless the C50R variant is specified.
Can C50 be welded?
Poor weldability (CE ≈ 0.6–0.7): preheat 250–350 °C, low-hydrogen consumables, interpass control and post-weld stress relief/temper are required to avoid HAZ martensite cracking.
Can C50 be formed, bent or molded?
Cold forming only in annealed/spheroidized condition with generous bend radii (≥2–3 t); hot forge at 1100–850 °C then normalize; oil- or water-quench from 820–860 °C, temper 150–650 °C to the required hardness.
What surface finishes work on C50?
Bare steel rusts quickly — protect by oiling, phosphating, black oxide, zinc or hard-chrome plating, or paint; grinds and polishes well after hardening.
C50 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 |
|---|---|---|
| CGB steel 50: 0.47-0.55 | 0.47 – 0.55 | 0.5 |
| SiEN: Si ≤0.40; GB: 0.17–0.37 | 0.17 – 0.4 | 0.25 |
| MnEN C50: 0.60–0.90; GB 50: 0.50–0.80 | 0.5 – 0.9 | 0.7 |
| PC50E/C50R ≤0.030; GB ≤0.035 | ≤ 0.05 | 0.02 |
| SC50E ≤0.035; C50R 0.020–0.040 | ≤ 0.05 | 0.02 |
| Crresidual; GB ≤0.25 | ≤ 0.4 | 0.15 |
| Niresidual; GB ≤0.30 | ≤ 0.4 | 0.1 |
| Moresidual | ≤ 0.1 | 0.02 |
| Curesidual (GB ≤0.25) | ≤ 0.25 | 0.1 |
| Fe | balance | — |
C50-AC — frequently asked
What is C50-AC used for?
C50-AC is typically used for crankshafts, gears, axles, high-strength bolts and rail wheels. In short: higher hardness than C40; wear-resistant after quench and temper; weldable only with preheat.
What is the yield strength of C50-AC?
C50-AC has a typical yield strength of 350 MPa (50.8 ksi) and a tensile strength of 600 MPa (87 ksi) — weaker than 74% of steel grades. Strength varies by condition: see the 11 listed tempers.
Is C50-AC easy to machine?
Reasonably — machinability is rated good (62/100, better than 89% of steel grades). Machines best at 180–220 HB (annealed/normalized); above 32 HRC use coated carbide, rigid setups and reduced feeds — no free-machining sulfur unless the C50R variant is specified.
Can C50-AC be welded?
With care — weldability is rated fair (36/100). Poor weldability (CE ≈ 0.6–0.7): preheat 250–350 °C, low-hydrogen consumables, interpass control and post-weld stress relief/temper are required to avoid HAZ martensite cracking.
What surface finishes work on C50-AC?
Bare steel rusts quickly — protect by oiling, phosphating, black oxide, zinc or hard-chrome plating, or paint; grinds and polishes well after hardening.
Can C50-AC be formed, bent or molded?
Cold forming only in annealed/spheroidized condition with generous bend radii (≥2–3 t); hot forge at 1100–850 °C then normalize; oil- or water-quench from 820–860 °C, temper 150–650 °C to the required hardness.
What is the maximum service temperature of C50-AC?
C50-AC is rated for continuous use to about 350°C (662 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between C50-N and C50 QT-Low?
N is the default condition — standard stocked/uniform-structure condition: balanced strength and machinability, good base for later Q&T or induction hardening. QT-Low: maximum hardness/wear resistance for thin sections, springs and tools; brittle, avoid impact and stress raisers. Yield strength is 425 MPa in N versus 1,600 MPa in QT-Low.
Sources
- EN 10083-2 Steels for quenching and tempering — Non-alloy steels (C50, C50E, C50R) — CEN (2006)
- JIS G 4051 Carbon steels for machine structural use (S50C) — JSA (2016)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels (AISI 1050 data) — ASM International (1990)
- ASM Handbook Vol.4 — Heat Treating / Vol.16 Machining — ASM International (1991)
- SAE J403 / SAE J1397 estimated mechanical properties of carbon steel bars — SAE International (2020)
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.