Steel 4118-SA (Spheroidize Annealed)
Heat-treated state
AISI/SAE 4118 · UNS G41180 · EN 20CrMo
Pick for cold heading, cold extrusion or deep-form gear blanks needing maximum ductility.
Values for the SA condition
Other 4118 tempers and conditions
4118 is listed in 8 conditions; see the grade overview at 4118.
Compare all 8 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
SAThis page Spheroidize Annealed | Pick for cold heading, cold extrusion or deep-form gear blanks needing maximum ductility. | 330 | 480 | 30 | 140 HB | 7.8 % IACS |
ANNDefault Annealed | Standard stocked bar condition for machining gear blanks before carburizing. | 350 | 530 | 26 | 149 HB | — |
Hardenability-guaranteed (H-band) grade | Order the H grade when Jominy end-quench hardenability must fall inside the SAE H-band for repeatable case/core response. | 355 | 540 | 25 | 149 HB | 7.8 % IACS |
Hot rolled | Cheapest mill condition for forging or re-heat-treatment stock; scaled surface, less uniform properties. | 380 | 570 | 24 | 163 HB | 7.8 % IACS |
Normalized | Use to homogenize forgings and refine grain before carburizing; better toughness uniformity than as-rolled. | 415 | 620 | 23 | 179 HB | — |
Cold drawn | Choose for close-tolerance bright bar and small shafts/pins where extra as-machined strength helps. | 540 | 640 | 13 | 187 HB | — |
Q&T | Direct-hardened condition for shafts and fasteners that need a tough medium-strength body without a case. | 660 | 860 | 18 | 25 HRC | — |
Carburized, hardened and tempered | The service condition for gears, splines and pins: hard wear-resistant case over a tough ~28–40 HRC core. | 760 | 1,000 | 12 | 60 HRC | — |
What is 4118-SA?
4118-SA is 4118 heat treated to SA — pick for cold heading, cold extrusion or deep-form gear blanks needing maximum ductility. 4118-SA has a yield strength of 330 MPa (47.9 ksi) and a tensile strength of 480 MPa (69.6 ksi) — weaker than 78% of steel grades. Elongation at break is 30% and the elastic modulus is 205 GPa (29.7 Msi). 4118-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). ANN is the default condition FabDigit quotes; SA is available on request or by drawing note.
Advantages
- Ductile — tolerates forming and impact — 30%, better than 93% of steel grades
- Low embodied carbon — 1.9 kg CO₂/kg, better than 92% of steel grades
- Forms and bends easily — 78/100, better than 91% of steel grades
- Easy to machine — 62/100, better than 89% of steel grades
Limitations
- Low strength — 330 MPa (47.9 ksi), worse than 78% of steel grades
4118-SA properties
Typical room-temperature values for 4118-SA; 22 are specific to this condition. Other listed values are 4118 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
4118-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).
Mechanical14
4118-SA has a yield strength of 330 MPa (47.9 ksi) and a tensile strength of 480 MPa (69.6 ksi) — weaker than 78% of steel grades. Elongation at break is 30% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
4118-SA is rated for continuous service to 400°C (752 °F). It conducts heat at 42 W/m·K (24.3 BTU/hr·ft·°F), worse than 56% of steel grades. Thermal expansion is 12.2 µm/m·K (6.78 µin/in·°F).
Electrical3
4118-SA conducts electricity at 7.8 % IACS, worse than 57% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of 4118-SA takes about 24 MJ of energy and emits 1.9 kg of CO₂ — less than 97% of steel grades. Typical recycled content is 30%.
Manufacturability7
4118-SA's machinability is good (62/100, better than 89% of steel grades); weldability good (62/100); formability very good (78/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 4118-SA
Is 4118 easy to machine?
Machine in the annealed or normalized state (~150–180 HB) with carbide at moderate speeds; finish-machine before carburizing since the 58–62 HRC case demands grinding or hard turning with CBN.
Can 4118 be welded?
Weldable in the low-carbon condition with low-hydrogen consumables and 150–250 °C preheat plus post-weld stress relief; never weld carburized surfaces.
Can 4118 be formed, bent or molded?
Good hot forgeability at 1150–1200 °C; cold heading and cold extrusion practical after spheroidize annealing, with normalizing afterwards to refine grain.
What surface finishes work on 4118?
No anodizing (ferrous); protect with oil, black oxide, manganese phosphate, zinc plating or nitrided/carburized-and-ground surfaces, and shot-peen gear roots to boost fatigue life.
4118 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 |
|---|---|---|
| C0.17–0.23 for 4118H | 0.18 – 0.23 | 0.2 |
| Mn | 0.7 – 0.9 | 0.8 |
| Si | 0.15 – 0.35 | 0.25 |
| Cr | 0.4 – 0.6 | 0.5 |
| Mo | 0.08 – 0.15 | 0.12 |
| P | ≤ 0.04 | 0.02 |
| S | ≤ 0.04 | 0.02 |
| Fe | balance | — |
4118-SA — frequently asked
What is 4118-SA used for?
4118-SA is typically used for gears, camshafts, small pins and clutch parts. In short: economical Cr-Mo carburizing steel; tough core, 58–62 HRC case; leaner alloy than 8620.
What is the yield strength of 4118-SA?
4118-SA has a typical yield strength of 330 MPa (47.9 ksi) and a tensile strength of 480 MPa (69.6 ksi) — weaker than 78% of steel grades. Strength varies by condition: see the 8 listed tempers.
Is 4118-SA easy to machine?
Reasonably — machinability is rated good (62/100, better than 89% of steel grades). Machine in the annealed or normalized state (~150–180 HB) with carbide at moderate speeds; finish-machine before carburizing since the 58–62 HRC case demands grinding or hard turning with CBN.
Can 4118-SA be welded?
Yes — weldability is rated good (62/100). Weldable in the low-carbon condition with low-hydrogen consumables and 150–250 °C preheat plus post-weld stress relief; never weld carburized surfaces.
What surface finishes work on 4118-SA?
No anodizing (ferrous); protect with oil, black oxide, manganese phosphate, zinc plating or nitrided/carburized-and-ground surfaces, and shot-peen gear roots to boost fatigue life.
Can 4118-SA be formed, bent or molded?
Good hot forgeability at 1150–1200 °C; cold heading and cold extrusion practical after spheroidize annealing, with normalizing afterwards to refine grain.
What is the maximum service temperature of 4118-SA?
4118-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 4118-ANN and 4118-CD?
ANN is the default condition — standard stocked bar condition for machining gear blanks before carburizing. CD: choose for close-tolerance bright bar and small shafts/pins where extra as-machined strength helps. Yield strength is 350 MPa in ANN versus 540 MPa in CD.
Sources
- SAE J404 — Chemical Compositions of SAE Alloy Steels — SAE International (2021)
- SAE J1268 — Hardenability Bands for Carbon and Alloy H Steels — SAE International (2019)
- ASTM A29/A29M — Steel Bars, Carbon and Alloy, Hot-Wrought — ASTM (2020)
- ASTM A322 — Steel Bars, Alloy, Standard Grades — ASTM (2020)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol.4A — Steel Heat Treating Fundamentals and Processes — ASM International (2013)
- ASM Handbook Vol.16 — Machining — ASM International (1989)
- GB/T 3077 — Alloy structural steels (20CrMo comparison) — SAC (2015)
- Mysteel / 1688 alloy structural steel bar price levels (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.