Steel SCr420
JIS SCr420 · EN 20Cr
SCr420 is a chromium case-hardening steel comparable to AISI 5120 and 20MnCr5, stocked hot-rolled, annealed, spheroidise-annealed, normalised, cold-drawn, quenched-and-tempered, carburised or carbonitrided.
Reference datasheet — SCr420 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 A condition
SCr420 tempers and conditions
SCr420 is supplied in 8 conditions, soft to hard. A is the default FabDigit quotes; the values on this page are for it.
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 | — |
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?
SCr420 is a chromium case-hardening steel comparable to AISI 5120 and 20MnCr5, stocked hot-rolled, annealed, spheroidise-annealed, normalised, cold-drawn, quenched-and-tempered, carburised or carbonitrided. In the default condition the core gives 350 MPa yield, 560 MPa tensile, 25 % elongation and 170 HB (87 HRB), with service to 400 °C. It is used for automotive gears, shafts and pins that need a hard case over a tough core, and it machines (60/100) and cold-forges (62/100) well before hardening. Carburising adds process cost and distortion control; SCr440 is the alternative when through-hardening is sufficient. SCr420 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). SCr420 has a yield strength of 350 MPa (50.8 ksi) and a tensile strength of 560 MPa (81.2 ksi) — weaker than 74% of steel grades. Elongation at break is 25% and the elastic modulus is 207 GPa (30 Msi).
What is SCr420 used for?
- automotive gears
- shafts
- pins
Advantages
- Forms and bends easily — 62/100, better than 78% of steel grades
- Ductile — tolerates forming and impact — 25%, better than 77% of steel grades
SCr420 properties
Typical room-temperature values for SCr420-A; bars are the position among steel grades.
Physical3
SCr420 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 has a yield strength of 350 MPa (50.8 ksi) and a tensile strength of 560 MPa (81.2 ksi) — weaker than 74% of steel grades. Elongation at break is 25% and the elastic modulus is 207 GPa (30 Msi).
Thermal6
SCr420 is rated for continuous service to 400°C (752 °F). It conducts heat at 44 W/m·K (25.4 BTU/hr·ft·°F), better than 57% of steel grades. Thermal expansion is 12.2 µm/m·K (6.78 µin/in·°F).
Electrical3
SCr420 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 SCr420 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's machinability is good (60/100, better than 83% of steel grades); weldability good (55/100); formability good (62/100).
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. SCr420 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with SCr420
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.
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 |
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.
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 SCr420 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
How much does SCr420 cost?
SCr420 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.
SCr420 — frequently asked
What is SCr420 used for?
SCr420 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?
SCr420 has a typical yield strength of 350 MPa (50.8 ksi) and a tensile strength of 560 MPa (81.2 ksi) — weaker than 74% of steel grades. Strength varies by condition: see the 8 listed tempers.
Is SCr420 easy to machine?
Reasonably — machinability is rated good (60/100, better than 83% 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 be welded?
Yes — weldability is rated good (55/100). 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?
No anodizing — protect with Mn/Zn phosphate, black oxide, zinc or Cr plating; shot peening after carburizing markedly raises bending fatigue life.
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 is the maximum service temperature of SCr420?
SCr420 is rated for continuous use to about 400°C (752 °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.
How much does SCr420 cost?
SCr420 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
- 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; 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.