Steel 4720
AISI/SAE 4720 · UNS G47200
4720 is a nickel-molybdenum case-hardening (carburizing) steel to AISI/SAE and UNS G47200, closely related to 4620 but with slightly higher nickel for improved core hardenability.
Reference datasheet — 4720 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 N condition
4720 tempers and conditions
4720 is supplied in 6 conditions, soft to hard. N 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 |
|---|---|---|---|---|---|---|
Solution annealed | Softest, most machinable and coldest-formable state; use before carburizing or for cold heading. | 350 | 550 | 28 | 163 HB | — |
Hot rolled | Cheapest mill condition for parts that will be fully carburized or re-heat-treated after rough machining. | 400 | 620 | 22 | 190 HB | 7.8 % IACS |
NDefault Normalized | Standard stocked bar condition: uniform fine grain, good machinability, ideal starting structure for carburizing. | 430 | 640 | 23 | 200 HB | 7.8 % IACS |
Cold drawn | Pick for close-tolerance shafting and screw-machine work where a bright finish and higher as-supplied strength help. | 570 | 690 | 15 | 210 HB | 7.8 % IACS |
Direct Q&T | Use when the low-carbon core strength/toughness after quench-and-temper (without case) must be quantified. | 780 | 1,000 | 14 | 32 HRC | — |
Carburized, quenched & tempered | The service condition for gears and pinions: hard wear-resistant case over a tough Ni-Mo core with high compressive residual stress. | 820 | 1,050 | 12 | 60 HRC | — |
What is 4720?
4720 is a nickel-molybdenum case-hardening (carburizing) steel to AISI/SAE and UNS G47200, closely related to 4620 but with slightly higher nickel for improved core hardenability. Engineers specify it for carburized gears and transmission parts that need a 58–62 HRC wear case over a tough core; it is stocked as hot-rolled, annealed, normalized and cold-drawn bar, with quench-and-tempered core and carburized conditions on file. Default-condition properties are 430 MPa yield, 640 MPa tensile, 23 % elongation and about 200 HB (93 HRB). It has no inherent corrosion resistance and must be finish-machined before carburizing; 4620 is the nearest alternative when core hardenability demands are lower. 4720 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). 4720 has a yield strength of 430 MPa (62.4 ksi) and a tensile strength of 640 MPa (92.8 ksi) — weaker than 51% of steel grades. Elongation at break is 23% and the elastic modulus is 205 GPa (29.7 Msi).
What is 4720 used for?
- Carburized transmission gears
- Differential pinions
- Gearbox input and output shafts
- Splined drive couplings
- Sprockets and chain wheels
- Pivot and wrist pins
4720 properties
Typical room-temperature values for 4720-N; bars are the position among steel grades.
Physical3
4720 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
4720 has a yield strength of 430 MPa (62.4 ksi) and a tensile strength of 640 MPa (92.8 ksi) — weaker than 51% of steel grades. Elongation at break is 23% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
4720 is rated for continuous service to 350°C (662 °F). It conducts heat at 43 W/m·K (24.8 BTU/hr·ft·°F), better than 51% of steel grades. Thermal expansion is 11.7 µm/m·K (6.5 µin/in·°F).
Electrical3
4720 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 4720 takes about 31 MJ of energy and emits 2.2 kg of CO₂ — more than 64% of steel grades. Typical recycled content is 30%.
Manufacturability7
4720's machinability is good (58/100, better than 75% of steel grades); weldability good (55/100); 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. 4720 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with 4720
Is 4720 easy to machine?
Machine green in the annealed/normalized state (~65 % of 1212) with carbide tooling; finish-grind gear teeth after carburizing since the 58–62 HRC case is essentially unmachinable.
Can 4720 be welded?
Weldable by GMAW/GTAW/SMAW with low-hydrogen filler, 200–260 °C preheat and post-weld stress relief; never weld a carburized surface.
Can 4720 be formed, bent or molded?
Hot forge 1100–1200 °C then normalize; cold heading and light bending only in the annealed condition.
4720 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 | 0.17 – 0.22 | 0.2 |
| Mn | 0.5 – 0.7 | 0.6 |
| Si | 0.15 – 0.35 | 0.25 |
| Ni | 0.9 – 1.2 | 1.05 |
| Cr | 0.35 – 0.55 | 0.45 |
| Mo | 0.15 – 0.25 | 0.2 |
| Pmax, SAE J404 bar | ≤ 0.04 | |
| Smax; H-band/resulfurized variants differ | ≤ 0.04 | |
| Fe | balance |
What surface finishes work on 4720?
No anodizing (ferrous) — protect with manganese/zinc phosphate + oil, black oxide, or zinc/nickel plating (bake to avoid hydrogen embrittlement after case hardening).
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 4720 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- UNS
- G47200
How much does 4720 cost?
4720 is a budget-cost steel ($), cheaper than about 90% 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.
4720 — frequently asked
What is 4720 used for?
4720 is typically used for carburized transmission gears, differential pinions, gearbox input and output shafts, splined drive couplings, sprockets and chain wheels and pivot and wrist pins. In short: higher nickel than 4620; tough core, 58–62 HRC case; ni-Mo gear steel.
What is the yield strength of 4720?
4720 has a typical yield strength of 430 MPa (62.4 ksi) and a tensile strength of 640 MPa (92.8 ksi) — weaker than 51% of steel grades. Strength varies by condition: see the 6 listed tempers.
Is 4720 easy to machine?
Reasonably — machinability is rated good (58/100, better than 75% of steel grades). Machine green in the annealed/normalized state (~65 % of 1212) with carbide tooling; finish-grind gear teeth after carburizing since the 58–62 HRC case is essentially unmachinable.
Can 4720 be welded?
Yes — weldability is rated good (55/100). Weldable by GMAW/GTAW/SMAW with low-hydrogen filler, 200–260 °C preheat and post-weld stress relief; never weld a carburized surface.
What surface finishes work on 4720?
No anodizing (ferrous) — protect with manganese/zinc phosphate + oil, black oxide, or zinc/nickel plating (bake to avoid hydrogen embrittlement after case hardening).
Can 4720 be formed, bent or molded?
Hot forge 1100–1200 °C then normalize; cold heading and light bending only in the annealed condition.
What is the maximum service temperature of 4720?
4720 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 4720-N and 4720 QT-CORE?
N is the default condition — standard stocked bar condition: uniform fine grain, good machinability, ideal starting structure for carburizing. QT-CORE: use when the low-carbon core strength/toughness after quench-and-temper (without case) must be quantified. Yield strength is 430 MPa in N versus 780 MPa in QT-CORE.
How much does 4720 cost?
4720 is a budget-cost steel ($), cheaper than about 90% 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 Carbon and Alloy H Steels — SAE International (2019)
- ASTM A29/A29M — Steel Bars, Carbon and Alloy, Hot-Wrought — ASTM International (2020)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol.4 — Heat Treating (Carburizing) — ASM International (1991)
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.