Steel SCr420-CN (Carbonitrided)
Heat-treated state
JIS SCr420 · EN 20Cr
Lower-temperature alternative for thin cases (0.2–0.6 mm) on small gears, washers and pins with less distortion.
Values for the CN condition
Other SCr420 tempers and conditions
SCr420 is listed in 8 conditions; see the grade overview at SCr420.
Compare all 8 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Spheroidize annealed | Choose for cold forging / cold extrusion of gear blanks and splined shafts. | 320 | 500 | 30 | 150 HB | 8 % IACS |
ADefault Solution annealed | Standard stock condition for machining green parts before carburizing. | 350 | 560 | 25 | 170 HB | — |
Hot rolled | Cheapest mill condition for bars that will be forged and fully heat treated later. | 390 | 620 | 22 | 185 HB | — |
Normalized | Refines forging grain structure and gives uniform machinability before carburizing. | 420 | 660 | 22 | 197 HB | — |
Cold drawn | Pick for precise-diameter shafting and automatic-lathe work where tighter tolerance and better finish are needed. | 560 | 680 | 12 | 200 HB | — |
Quenched and tempered | Use for shafts and fasteners that need through strength without a carburized case; JIS core-property condition. | 700 | 900 | 17 | 29 HRC | — |
CNThis page Carbonitrided | Lower-temperature alternative for thin cases (0.2–0.6 mm) on small gears, washers and pins with less distortion. | 700 | 1,000 | 11 | 59 HRC | 7.4 % IACS |
Carburized and hardened | The service condition for gears and splines: hard wear/pitting-resistant case over a tough core. | 850 | 1,100 | 11 | 60 HRC | — |
What is SCr420-CN?
SCr420-CN is SCr420 heat treated to CN — lower-temperature alternative for thin cases (0.2–0.6 mm) on small gears, washers and pins with less distortion. SCr420-CN has a yield strength of 700 MPa (102 ksi) and a tensile strength of 1,000 MPa (145 ksi) — stronger than 81% of steel grades. Elongation at break is 11% and the elastic modulus is 207 GPa (30 Msi). SCr420-CN 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). A is the default condition FabDigit quotes; CN is available on request or by drawing note.
Advantages
- High strength — 700 MPa (102 ksi), better than 81% of steel grades
Limitations
- Difficult to machine — 10/100, worse than 99% of steel grades
- Limited formability — 5/100, worse than 99% of steel grades
- Limited service temperature — 180°C (356 °F), worse than 98% of steel grades
- Difficult to weld — 15/100, worse than 91% of steel grades
- Limited ductility — 11%, worse than 89% of steel grades
SCr420-CN properties
Typical room-temperature values for SCr420-CN; 21 are specific to this condition. Other listed values are SCr420 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
SCr420-CN 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
SCr420-CN has a yield strength of 700 MPa (102 ksi) and a tensile strength of 1,000 MPa (145 ksi) — stronger than 81% of steel grades. Elongation at break is 11% and the elastic modulus is 207 GPa (30 Msi).
Thermal6
SCr420-CN is rated for continuous service to 180°C (356 °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
SCr420-CN conducts electricity at 7.4 % IACS, worse than 70% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of SCr420-CN takes about 27 MJ of energy and emits 2.1 kg of CO₂ — less than 59% of steel grades. Typical recycled content is 30%.
Manufacturability8
SCr420-CN's machinability is not recommended (10/100, worse than 99% of steel grades); weldability poor (15/100); formability not recommended (5/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with SCr420-CN
Is SCr420 easy to machine?
Machine green in the annealed or normalized state (~60 % of 1212); after carburizing only grinding, honing or hard turning with CBN is practical.
Can SCr420 be welded?
Weldable before heat treatment with 100–200 °C preheat and low-hydrogen consumables; welding carburized parts is not recommended due to case cracking.
Can SCr420 be formed, bent or molded?
Hot forges readily at 1100–1200 °C; spheroidize annealed bar cold-forges and cold-extrudes well for gear and shaft blanks.
What surface finishes work on SCr420?
No anodizing — protect with Mn/Zn phosphate, black oxide, zinc or Cr plating; shot peening after carburizing markedly raises bending fatigue life.
SCr420 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 |
|---|---|---|
| CJIS G4053 | 0.18 – 0.23 | 0.2 |
| Si | 0.15 – 0.35 | 0.25 |
| Mn | 0.6 – 0.9 | 0.75 |
| P | ≤ 0.03 | — |
| S | ≤ 0.03 | — |
| Cr | 0.9 – 1.2 | 1.05 |
| Niresidual max | ≤ 0.25 | — |
| Curesidual max | ≤ 0.3 | — |
| Moresidual, not intentionally added | ≤ 0.08 | — |
| Fe | balance | — |
SCr420-CN — frequently asked
What is SCr420-CN used for?
SCr420-CN is typically used for automotive gears, shafts and pins. In short: standard carburising gear steel; 5120 / 20MnCr5 equivalent; cold-forgeable case-hardening bar.
What is the yield strength of SCr420-CN?
SCr420-CN has a typical yield strength of 700 MPa (102 ksi) and a tensile strength of 1,000 MPa (145 ksi) — stronger than 81% of steel grades. Strength varies by condition: see the 8 listed tempers.
Is SCr420-CN easy to machine?
Not especially — machinability is rated not recommended (10/100, worse than 99% of steel grades). Machine green in the annealed or normalized state (~60 % of 1212); after carburizing only grinding, honing or hard turning with CBN is practical.
Can SCr420-CN be welded?
Not readily — weldability is rated poor (15/100). Weldable before heat treatment with 100–200 °C preheat and low-hydrogen consumables; welding carburized parts is not recommended due to case cracking.
What surface finishes work on SCr420-CN?
No anodizing — protect with Mn/Zn phosphate, black oxide, zinc or Cr plating; shot peening after carburizing markedly raises bending fatigue life.
Can SCr420-CN be formed, bent or molded?
Hot forges readily at 1100–1200 °C; spheroidize annealed bar cold-forges and cold-extrudes well for gear and shaft blanks.
What is the maximum service temperature of SCr420-CN?
SCr420-CN is rated for continuous use to about 180°C (356 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between SCr420-A and SCr420-CH?
A is the default condition — standard stock condition for machining green parts before carburizing. CH: the service condition for gears and splines: hard wear/pitting-resistant case over a tough core. Yield strength is 350 MPa in A versus 850 MPa in CH.
Sources
- JIS G 4053 — Low-alloyed steels for machine structural use — JSA (2016)
- ASTM A29/A29M and SAE J404 (AISI 5120) — ASTM / SAE (2020)
- GB/T 3077 (20Cr) — SAC (2015)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol.4A — Steel Heat Treating Fundamentals (carburizing) — ASM International (2013)
- SMM / Mysteel (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.