Steel 4720-N (Normalized)
Heat-treated state · default condition
AISI/SAE 4720 · UNS G47200
Standard stocked bar condition: uniform fine grain, good machinability, ideal starting structure for carburizing.
Values for the N condition
Other 4720 tempers and conditions
4720 is listed in 6 conditions; see the grade overview at 4720.
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 |
NDefaultThis page 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-N?
4720-N is 4720 heat treated to N — standard stocked bar condition: uniform fine grain, good machinability, ideal starting structure for carburizing. 4720-N 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). 4720-N 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-N properties
Typical room-temperature values for 4720-N; 22 are specific to this condition. Other listed values are 4720 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
4720-N 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-N 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-N 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-N 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-N 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-N'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. Confirm any required mill or lot documentation when quoting.
Working with 4720-N
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.
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).
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 | — |
4720-N — frequently asked
What is 4720-N used for?
4720-N 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-N?
4720-N 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-N 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-N 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-N?
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-N 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-N?
4720-N 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.
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. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.