Steel 4320-CR (Cold rolled)
Supply condition
AISI/SAE 4320 · UNS G43200 · JIS SNCM420
Thin strip/sheet form for stamped, carburized parts needing good surface and tight thickness.
Values for the CR condition
Other 4320 tempers and conditions
4320 is listed in 7 conditions; see the grade overview at 4320.
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 | — |
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 | — |
CRThis page 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-CR?
4320-CR is 4320 supplied in the CR condition — thin strip/sheet form for stamped, carburized parts needing good surface and tight thickness. 4320-CR has a yield strength of 550 MPa (79.8 ksi) and a tensile strength of 700 MPa (102 ksi) — stronger than 71% of steel grades. Elongation at break is 12% and the elastic modulus is 205 GPa (29.7 Msi). 4320-CR 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; CR is available on request or by drawing note.
Limitations
- Limited ductility — 12%, worse than 84% of steel grades
- Limited service temperature — 300°C (572 °F), worse than 78% of steel grades
4320-CR properties
Typical room-temperature values for 4320-CR; 22 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-CR 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-CR has a yield strength of 550 MPa (79.8 ksi) and a tensile strength of 700 MPa (102 ksi) — stronger than 71% of steel grades. Elongation at break is 12% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
4320-CR is rated for continuous service to 300°C (572 °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-CR 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-CR 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-CR's machinability is fair (52/100, better than 52% of steel grades); weldability fair (38/100); formability fair (35/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 4320-CR
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-CR — frequently asked
What is 4320-CR used for?
4320-CR is typically used for gears, pins and shafts. In short: carburizing Ni-Cr-Mo bar.
What is the yield strength of 4320-CR?
4320-CR has a typical yield strength of 550 MPa (79.8 ksi) and a tensile strength of 700 MPa (102 ksi) — stronger than 71% of steel grades. Strength varies by condition: see the 7 listed tempers.
Is 4320-CR easy to machine?
Reasonably — machinability is rated fair (52/100, better than 52% 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-CR be welded?
With care — weldability is rated fair (38/100). Restricted weldability — preheat 200–300 °C, use low-hydrogen Ni-Mo filler and PWHT; never weld after carburizing.
What surface finishes work on 4320-CR?
No anodizing; protect with oil, black oxide, manganese phosphate, or zinc/zinc-nickel plating with post-plate bake to avoid hydrogen embrittlement.
Can 4320-CR 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-CR?
4320-CR is rated for continuous use to about 300°C (572 °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-CR?
Yes — 4320-CR 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.