Steel SCM420 · supply condition · default condition
Steel SCM420-HR
Properties of the HR condition, compared with the other SCM420 tempers.
Standard stock condition for bar and billet destined for machining, forging or carburizing.
What is SCM420-HR?
SCM420-HR is SCM420 supplied in the HR condition — standard stock condition for bar and billet destined for machining, forging or carburizing. SCM420-HR has a yield strength of 440 MPa (63.8 ksi) and a tensile strength of 660 MPa (95.7 ksi) — stronger than 51% of steel grades. Elongation at break is 22% and the elastic modulus is 207 GPa (30 Msi). SCM420-HR 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).
Advantages
- Easy to machine — 60/100, better than 83% of steel grades
Limitations
- Low fracture toughness — 65 MPa·√m (59.2 ksi·√in), worse than 76% of steel grades
SCM420-HR properties
Typical room-temperature values for SCM420-HR — 10 properties are specific to this condition; the rest are grade-level values shared by every SCM420 temper. Each bar shows where the value sits among the steel grades in FabDigit's library — further right is higher.
Physical3
SCM420-HR 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).
Mechanical14
SCM420-HR has a yield strength of 440 MPa (63.8 ksi) and a tensile strength of 660 MPa (95.7 ksi) — stronger than 51% of steel grades. Elongation at break is 22% and the elastic modulus is 207 GPa (30 Msi).
Thermal6
SCM420-HR is rated for continuous service to 400°C (752 °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
SCM420-HR conducts electricity at 7.8 % IACS, worse than 58% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of SCM420-HR takes about 30 MJ of energy and emits 2.3 kg of CO₂ — more than 55% of steel grades. Typical recycled content is 30%.
Manufacturability7
SCM420-HR's machinability is good (60/100, better than 83% of steel grades); weldability good (55/100); formability good (60/100).
Common Calculations5
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Other SCM420 tempers and conditions
SCM420 is also supplied in 6 other conditions. The full side-by-side table is on the SCM420 overview.
- HRDefaultStandard stock condition for bar and billet destined for machining, forging or carburizing.440 MPa yield · 190 HB
- CarburizedThe intended service condition for gears and pinions — hard wear-resistant case over a tough Cr-Mo core.900 MPa yield · 60 HRC
- Q&TThrough-hardened condition for shafts and fasteners where core strength, not surface wear, governs.760 MPa yield · 31 HRC
- CDCold-drawn bar giving close size tolerance, bright finish and higher as-supplied strength for screw-machine work.620 MPa yield · 225 HB
- NormalizedUniform fine-grain structure for consistent machining and predictable response to carburizing.470 MPa yield · 207 HB
- AnnealedSoftest condition — pick it for cold forging, deep machining or heavy upsetting before carburizing.360 MPa yield · 163 HB
Working with SCM420-HR
Is SCM420 easy to machine?
Machine in the annealed or normalized state (≈62 % of AISI 1212); carbide inserts, 120–180 m/min turning, finish-grind after carburizing to hold size.
Can SCM420 be welded?
Weldable with low-hydrogen consumables at CE ≈ 0.55: preheat 150–250 °C, control interpass, and PWHT at 600–650 °C; never weld a carburized surface.
Can SCM420 be formed, bent or molded?
Spheroidize-anneal for cold heading and cold forging; hot forge 1100–1200 °C and finish above 900 °C, then normalize before machining.
What surface finishes work on SCM420?
No anodizing — protect with black oxide, manganese phosphate, zinc or Ni plating; after carburizing use shot peening plus grinding for maximum bending fatigue life.
SCM420 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 G 4053 | 0.18 – 0.23 | 0.2 |
| Si | 0.15 – 0.35 | 0.25 |
| Mn | 0.6 – 0.85 | 0.75 |
| P | ≤ 0.03 | — |
| S | ≤ 0.03 | — |
| Cr | 0.9 – 1.2 | 1.05 |
| Mo | 0.15 – 0.3 | 0.22 |
| Niresidual max | ≤ 0.25 | — |
| Curesidual max | ≤ 0.3 | — |
| Fe | balance | — |
SCM420-HR — frequently asked
What is SCM420-HR used for?
SCM420-HR is typically used for gears, industrial drive shafts and pins. In short: carburizing Cr-Mo bar.
What is the yield strength of SCM420-HR?
SCM420-HR has a typical yield strength of 440 MPa (63.8 ksi) and a tensile strength of 660 MPa (95.7 ksi) — stronger than 51% of steel grades. Strength varies by condition: see the 7 listed tempers.
Is SCM420-HR easy to machine?
Reasonably — machinability is rated good (60/100, better than 83% of steel grades). Machine in the annealed or normalized state (≈62 % of AISI 1212); carbide inserts, 120–180 m/min turning, finish-grind after carburizing to hold size.
Can SCM420-HR be welded?
Yes — weldability is rated good (55/100). Weldable with low-hydrogen consumables at CE ≈ 0.55: preheat 150–250 °C, control interpass, and PWHT at 600–650 °C; never weld a carburized surface.
What surface finishes work on SCM420-HR?
No anodizing — protect with black oxide, manganese phosphate, zinc or Ni plating; after carburizing use shot peening plus grinding for maximum bending fatigue life.
Can SCM420-HR be formed, bent or molded?
Spheroidize-anneal for cold heading and cold forging; hot forge 1100–1200 °C and finish above 900 °C, then normalize before machining.
What is the maximum service temperature of SCM420-HR?
SCM420-HR 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 SCM420-HR and SCM420-CD?
HR is the default condition — standard stock condition for bar and billet destined for machining, forging or carburizing. CD: cold-drawn bar giving close size tolerance, bright finish and higher as-supplied strength for screw-machine work. Yield strength is 440 MPa in HR versus 620 MPa in CD.
Can FabDigit make parts in SCM420-HR?
Yes — SCM420-HR is available for CNC machining and sheet metal with instant online pricing. Upload a STEP file to get a price and a DFM check.
Sources
- JIS G 4053 — Low-alloyed steels for machine structural use — JSA (2016)
- ASTM A29/A29M and SAE J404 (4118/4120 equivalence) — ASTM / SAE (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 Cr-Mo steels) — ASM International (1991)
- GB/T 3077 — (20CrMo / 20CrMnMo comparison grades) — SAC (2015)
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.