Steel 4718
AISI/SAE 4718 · UNS G47180
4718 is a nickel-chromium-molybdenum carburizing steel (UNS G47180) that balances hardenability, core toughness and fatigue resistance for demanding gear applications.
Reference datasheet — 4718 is not in the instant-quote catalog. Upload your part and an engineer will quote it in this grade or suggest the closest stocked equivalent.
Values for the A condition
4718 tempers and conditions
4718 is supplied in 6 conditions, soft to hard. A is the default FabDigit quotes; the values on this page are for it.
Compare all 6 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
ADefault Solution annealed | Softest, most machinable condition — the standard stock form for gear blanks that will be carburized. | 400 | 585 | 27 | 170 HB | — |
Hot rolled | Mill-supplied as-rolled bar for parts that will be normalized or carburized after rough machining. | 460 | 700 | 22 | 207 HB | — |
Normalized | Uniform fine-grain structure for dimensional stability and consistent case depth before carburizing. | 480 | 725 | 22 | 217 HB | — |
Cold drawn | Cold-drawn bar for close size tolerance and better as-machined finish on small shafts and pins. | 640 | 760 | 15 | 229 HB | — |
direct quenched and tempered (through hardened core) | Through-hardened condition for shafts and non-carburized parts needing high core strength with good toughness. | 830 | 1,000 | 17 | 32 HRC | — |
Carburized, quenched & tempered | The service condition for gears and races: hard wear-resistant case with compressive residual stress over a tough alloy core. | 1,000 | 1,250 | 12 | 60 HRC | — |
What is 4718?
4718 is a nickel-chromium-molybdenum carburizing steel (UNS G47180) that balances hardenability, core toughness and fatigue resistance for demanding gear applications. It is supplied as hot-rolled, annealed, normalized and cold-drawn bar and forging stock, then carburized to 58–62 HRC or quenched and tempered to 30–34 HRC; annealed properties are about 400 MPa yield, 585 MPa tensile, 27 % elongation and 170 HB. Weldability is limited and requires preheat plus immediate tempering, and the steel offers no corrosion resistance, so plating, phosphating or oiling is needed. 8620 is the lower-cost alternative where hardenability demands are lighter. 4718 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). 4718 has a yield strength of 400 MPa (58 ksi) and a tensile strength of 585 MPa (84.8 ksi) — weaker than 60% of steel grades. Elongation at break is 27% and the elastic modulus is 205 GPa (29.7 Msi).
What is 4718 used for?
- heavy-duty gears
- pinions
- carburized power-transmission shafts
Advantages
- Ductile — tolerates forming and impact — 27%, better than 86% of steel grades
Limitations
- Limited service temperature — 200°C (392 °F), worse than 93% of steel grades
4718 properties
Typical room-temperature values for 4718-A; bars are the position among steel grades.
Physical3
4718 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).
Mechanical13
4718 has a yield strength of 400 MPa (58 ksi) and a tensile strength of 585 MPa (84.8 ksi) — weaker than 60% of steel grades. Elongation at break is 27% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
4718 is rated for continuous service to 200°C (392 °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
4718 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 4718 takes about 32 MJ of energy and emits 2.3 kg of CO₂ — more than 70% of steel grades. Typical recycled content is 30%.
Manufacturability7
4718's machinability is good (55/100, better than 62% of steel grades); weldability fair (45/100); formability good (55/100).
Common Calculations5
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the steel family
Yield strength against density for every steel grade FabDigit runs. 4718 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with 4718
Is 4718 easy to machine?
Machine in the annealed or normalized state (≈65 % of 1212) with carbide tooling and generous coolant; leave grinding stock because carburizing causes distortion.
Can 4718 be welded?
Weldable with low-hydrogen consumables but requires 200–300 °C preheat and immediate temper; avoid welding on carburized surfaces.
Can 4718 be formed, bent or molded?
Hot forge 1150–1200 °C and normalize afterwards; cold forming is limited to mild bending/upsetting in the annealed condition.
4718 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 | 0.16 – 0.21 | 0.19 |
| Mn | 0.7 – 0.9 | 0.8 |
| Si | 0.15 – 0.35 | 0.25 |
| Ni | 0.9 – 1.2 | 1.05 |
| Cr | 0.35 – 0.55 | 0.45 |
| Mo | 0.3 – 0.4 | 0.35 |
| P | ≤ 0.04 | |
| S | ≤ 0.04 | |
| Fe | balance |
What surface finishes work on 4718?
Case surfaces are typically hard-ground or honed; uncarburized areas take black oxide, manganese phosphate, zinc or nickel plating (bake to avoid hydrogen embrittlement).
Surface treatments FabDigit runs on steel parts — pick them in the quote configurator or call them out on the drawing. Each links to its datasheet in the surface-finish library (thickness, specs, call-out, material verdicts).
Organic Coating
Black / Phosphate
Thermal Spray
Equivalent designations
Standards and trade names that resolve to Steel 4718 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- UNS
- G47180
How much does 4718 cost?
4718 is a standard-cost steel ($$), cheaper than about 71% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
4718 — frequently asked
What is 4718 used for?
4718 is typically used for heavy-duty gears, pinions and carburized power-transmission shafts. In short: ni-Cr-Mo carburizing grade; alloy-rich 8620 alternative; fatigue-resistant gear steel.
What is the yield strength of 4718?
4718 has a typical yield strength of 400 MPa (58 ksi) and a tensile strength of 585 MPa (84.8 ksi) — weaker than 60% of steel grades. Strength varies by condition: see the 6 listed tempers.
Is 4718 easy to machine?
Reasonably — machinability is rated good (55/100, better than 62% of steel grades). Machine in the annealed or normalized state (≈65 % of 1212) with carbide tooling and generous coolant; leave grinding stock because carburizing causes distortion.
Can 4718 be welded?
With care — weldability is rated fair (45/100). Weldable with low-hydrogen consumables but requires 200–300 °C preheat and immediate temper; avoid welding on carburized surfaces.
What surface finishes work on 4718?
Case surfaces are typically hard-ground or honed; uncarburized areas take black oxide, manganese phosphate, zinc or nickel plating (bake to avoid hydrogen embrittlement).
Can 4718 be formed, bent or molded?
Hot forge 1150–1200 °C and normalize afterwards; cold forming is limited to mild bending/upsetting in the annealed condition.
What is the maximum service temperature of 4718?
4718 is rated for continuous use to about 200°C (392 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 4718-A and 4718-CD?
A is the default condition — softest, most machinable condition — the standard stock form for gear blanks that will be carburized. CD: cold-drawn bar for close size tolerance and better as-machined finish on small shafts and pins. Yield strength is 400 MPa in A versus 640 MPa in CD.
How much does 4718 cost?
4718 is a standard-cost steel ($$), cheaper than about 71% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Sources
- SAE J404 — Chemical Compositions of SAE Alloy Steels — SAE International (2021)
- SAE J1268 — Hardenability Bands for Carburizing Steels (4718H) — SAE International (2019)
- ASTM A29/A29M — General Requirements for 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.4A — Steel Heat Treating Fundamentals and Processes (carburizing) — ASM International (2013)
- Mysteel / SMM (2025)
Property data is compiled from published supplier and standards handbooks and normalised for comparison; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.