Steel 4118H
Grade
AISI/SAE 4118 · UNS G41180 · EN 20CrMo
4118H = 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.
Values for the 4118H 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 |
|---|---|---|---|---|---|---|
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 | — |
4118HThis page 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 4118H?
4118H is 4118 in the 4118H grade — order the H grade when Jominy end-quench hardenability must fall inside the SAE H-band for repeatable case/core response. 4118H has a yield strength of 355 MPa (51.5 ksi) and a tensile strength of 540 MPa (78.3 ksi) — weaker than 73% of steel grades. Elongation at break is 25% and the elastic modulus is 205 GPa (29.7 Msi). 4118H 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; 4118H is available on request or by drawing note.
Advantages
- Low embodied carbon — 1.9 kg CO₂/kg, better than 92% of steel grades
- Ductile — tolerates forming and impact — 25%, better than 77% of steel grades
4118H properties
Typical room-temperature values for 4118H; 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
4118H 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
4118H has a yield strength of 355 MPa (51.5 ksi) and a tensile strength of 540 MPa (78.3 ksi) — weaker than 73% of steel grades. Elongation at break is 25% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
4118H 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
4118H 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 4118H 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
4118H's machinability is good (60/100, better than 83% of steel grades); weldability good (60/100); formability good (58/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 4118H
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 | — |
4118H — frequently asked
What is 4118H used for?
4118H 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 4118H?
4118H has a typical yield strength of 355 MPa (51.5 ksi) and a tensile strength of 540 MPa (78.3 ksi) — weaker than 73% of steel grades. Strength varies by condition: see the 8 listed tempers.
Is 4118H easy to machine?
Reasonably — machinability is rated good (60/100, better than 83% 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 4118H be welded?
Yes — weldability is rated good (60/100). 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 4118H?
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 4118H 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 4118H?
4118H 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.