Steel 4320 Annealed
Temper
AISI/SAE 4320 · UNS G43200 · JIS SNCM420
Softest condition; pick it for heavy machining, deep hobbing or cold forming before carburizing.
Values for the Annealed condition
Other 4320 tempers and conditions
4320 is listed in 7 conditions; see the grade overview at 4320.
- HR
- Annealed
- Normalized
- CR
- CD
- Q&T
- Carburized
Compare all 7 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
HRDefault Hot rolled | Standard stock form for carburizing-grade bar that will be machined and then heat treated. | 415 | 640 | 22 | 187 HB | — |
AnnealedThis page full anneal ~840–870 °C, furnace cool | Softest condition; pick it for heavy machining, deep hobbing or cold forming before carburizing. | 425 | 580 | 29 | 163 HB | — |
~895 °C, air cool | Refines grain and homogenizes forgings/bar before carburizing; best pre-heat-treat condition for dimensional stability. | 464 | 793 | 21 | 21 HRC | — |
Cold rolled | Thin strip/sheet form for stamped, carburized parts needing good surface and tight thickness. | 550 | 700 | 12 | 15 HRC | 7.8 % IACS |
Cold drawn | Choose for close-tolerance, bright-surface bar that needs minimal turning before carburizing. | 620 | 745 | 15 | 217 HB | — |
Quenched and tempered | Direct-hardened condition for shafts and non-carburized parts needing high core strength with good toughness. | 900 | 1,080 | 15 | 34 HRC | — |
case 58–62 HRC, core ~30–40 HRC | The intended service condition: hard wear/contact-fatigue-resistant case over a tough Ni-Mo core for gears and bearing races. | 1,000 | 1,200 | 12 | 60 HRC | — |
What is 4320 Annealed?
4320 Annealed is 4320 in the Annealed temper — softest condition; pick it for heavy machining, deep hobbing or cold forming before carburizing. 4320 Annealed has a yield strength of 425 MPa (61.6 ksi) and a tensile strength of 580 MPa (84.1 ksi) — weaker than 52% of steel grades. Elongation at break is 29% and the elastic modulus is 205 GPa (29.7 Msi). 4320 Annealed 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). HR is the default condition FabDigit quotes; Annealed is available on request or by drawing note.
Advantages
- Ductile — tolerates forming and impact — 29%, better than 91% of steel grades
4320 Annealed properties
Typical room-temperature values for 4320 Annealed; 12 are specific to this condition. Other listed values are 4320 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
4320 Annealed 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).
Mechanical13
4320 Annealed has a yield strength of 425 MPa (61.6 ksi) and a tensile strength of 580 MPa (84.1 ksi) — weaker than 52% of steel grades. Elongation at break is 29% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
4320 Annealed is rated for continuous service to 350°C (662 °F). It conducts heat at 44 W/m·K (25.4 BTU/hr·ft·°F), better than 57% of steel grades. Thermal expansion is 11.7 µm/m·K (6.5 µin/in·°F).
Electrical2
4320 Annealed has an electrical resistivity of 2.2×10⁻⁷ Ω·m.
Chemical & Environmental3
Corrosion resistance is not recommended (11/100), worse than 73% of steel grades.
Sustainability4
Producing a kilogram of 4320 Annealed takes about 31 MJ of energy and emits 2.3 kg of CO₂ — more than 64% of steel grades. Typical recycled content is 30%.
Manufacturability7
4320 Annealed's machinability is good (58/100, better than 75% of steel grades); weldability fair (45/100); formability good (60/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 4320 Annealed
Is 4320 easy to machine?
Machine in the annealed or normalized condition with carbide tooling and rigid setups; leave grind stock because carburize-quench distorts, and finish-grind the case.
Can 4320 be welded?
Restricted weldability — preheat 200–300 °C, use low-hydrogen Ni-Mo filler and PWHT; never weld after carburizing.
Can 4320 be formed, bent or molded?
Cold-form only in the annealed state and with generous radii; hot forge 1150–1200 °C, finish above 900 °C and normalize afterwards.
What surface finishes work on 4320?
No anodizing; protect with oil, black oxide, manganese phosphate, or zinc/zinc-nickel plating with post-plate bake to avoid hydrogen embrittlement.
4320 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 | 0.45 – 0.65 | 0.55 |
| Si | 0.15 – 0.35 | 0.25 |
| Ni | 1.65 – 2 | 1.82 |
| Cr | 0.4 – 0.6 | 0.5 |
| Mo | 0.2 – 0.3 | 0.25 |
| P | ≤ 0.04 | |
| Smax; 4320H/E-grades tighter | ≤ 0.04 | |
| Fe | balance |
4320 Annealed — frequently asked
What is 4320 Annealed used for?
4320 Annealed is typically used for gears, pins and shafts. In short: carburizing Ni-Cr-Mo bar.
What is the yield strength of 4320 Annealed?
4320 Annealed has a typical yield strength of 425 MPa (61.6 ksi) and a tensile strength of 580 MPa (84.1 ksi) — weaker than 52% of steel grades. Strength varies by condition: see the 7 listed tempers.
Is 4320 Annealed easy to machine?
Reasonably — machinability is rated good (58/100, better than 75% of steel grades). Machine in the annealed or normalized condition with carbide tooling and rigid setups; leave grind stock because carburize-quench distorts, and finish-grind the case.
Can 4320 Annealed be welded?
With care — weldability is rated fair (45/100). Restricted weldability — preheat 200–300 °C, use low-hydrogen Ni-Mo filler and PWHT; never weld after carburizing.
What surface finishes work on 4320 Annealed?
No anodizing; protect with oil, black oxide, manganese phosphate, or zinc/zinc-nickel plating with post-plate bake to avoid hydrogen embrittlement.
Can 4320 Annealed be formed, bent or molded?
Cold-form only in the annealed state and with generous radii; hot forge 1150–1200 °C, finish above 900 °C and normalize afterwards.
What is the maximum service temperature of 4320 Annealed?
4320 Annealed 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 4320-HR and 4320-CD?
HR is the default condition — standard stock form for carburizing-grade bar that will be machined and then heat treated. CD: choose for close-tolerance, bright-surface bar that needs minimal turning before carburizing. Yield strength is 415 MPa in HR versus 620 MPa in CD.
Can FabDigit make parts in 4320 Annealed?
Yes — 4320 Annealed is available for CNC machining and sheet metal; every part is priced by an engineer rather than instantly. Upload a STEP file to get a price and a DFM check.
Sources
- SAE J404 — Chemical Compositions of SAE Alloy Steels — SAE International (2021)
- ASTM A29/A29M — 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.4 — Heat Treating (carburizing of Ni-Cr-Mo steels) — ASM International (1991)
- GB/T 3077 (20CrNi2Mo) — SAC (2015)
- JIS G 4053 (SNCM420) — JSA (2016)
- Mysteel / SMM alloy bar and nickel price references — Mysteel, SMM (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.