Steel SCM440 Nitrided
Finish state
JIS SCM440 · EN 42CrMo4
Low-distortion hard case (~0.2–0.5 mm, 550–650 HV) for wear and fatigue-critical shafts and screws.
Values for the Nitrided condition
Other SCM440 tempers and conditions
SCM440 is listed in 11 conditions; see the grade overview at SCM440.
Compare all 11 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
full/spheroidize annealed, softest condition | Choose for heavy machining, cold forming or deep-hole drilling before final hardening. | 415 | 655 | 25 | 197 HB | — |
Cold rolled | Thin strip/sheet stock with tight thickness and a clean surface, for stamped parts later hardened. | 550 | 750 | 13 | 17 HRC | 7.8 % IACS |
HRDefault Hot rolled | Cheapest stock form for parts that will be machined then heat treated by the fabricator. | 590 | 880 | 17 | 25 HRC | — |
860–880 °C air cooled | Uniform fine grain and mid-range strength; used as pre-treatment before machining/hardening or as final state for low-stress parts. | 655 | 1,020 | 17.5 | 32 HRC | — |
Quenched and high-temperature tempered | Maximum toughness / NACE-friendly hardness cap for pressure and downhole components. | 720 | 860 | 20 | 24 HRC | — |
Cold drawn | Pick for near-net-size shafts and turned parts needing good surface finish and straightness without further grinding. | 750 | 900 | 12 | 26 HRC | — |
NitridedThis page Q&T then gas/plasma nitrided (500–540 °C) | Low-distortion hard case (~0.2–0.5 mm, 550–650 HV) for wear and fatigue-critical shafts and screws. | 850 | 980 | 12 | 55 HRC | 7.8 % IACS |
Quenched and tempered | Standard supply condition for shafts, gears and machine parts needing balanced strength and toughness. | 880 | 1,000 | 16 | 30 HRC | — |
Induction hardened | For journals, splines and guideways needing a wear-resistant 52–58 HRC case over a tough Q&T core. | 880 | 1,000 | 14 | 55 HRC | 7.8 % IACS |
Quenched and medium-temperature tempered | Higher-strength shafts, high-tensile bolting and moulds where toughness is still needed. | 1,060 | 1,180 | 14 | 36 HRC | — |
Quenched and low-temperature tempered | Highest strength/wear condition for pins, dies and rams; accept low impact toughness and hydrogen-embrittlement risk when plating. | 1,280 | 1,400 | 11 | 42 HRC | — |
What is SCM440 Nitrided?
SCM440 Nitrided is SCM440 supplied in the Nitrided condition — low-distortion hard case (~0.2–0.5 mm, 550–650 HV) for wear and fatigue-critical shafts and screws. SCM440 Nitrided has a yield strength of 850 MPa (123 ksi) and a tensile strength of 980 MPa (142 ksi) — stronger than 88% of steel grades. Elongation at break is 12% and the elastic modulus is 210 GPa (30.5 Msi). SCM440 Nitrided has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,416°C (2,581 °F). HR is the default condition FabDigit quotes; Nitrided is available on request or by drawing note.
Advantages
- High strength — 850 MPa (123 ksi), better than 88% of steel grades
- High service temperature — 450°C (842 °F), better than 86% of steel grades
- Polishes to a fine finish — 65/100, better than 78% of steel grades
Limitations
- Difficult to weld — 5/100, worse than 100% of steel grades
- Limited formability — 3/100, worse than 99% of steel grades
- Difficult to machine — 15/100, worse than 98% of steel grades
- Limited ductility — 12%, worse than 84% of steel grades
SCM440 Nitrided properties
Typical room-temperature values for SCM440 Nitrided; 22 are specific to this condition. Other listed values are SCM440 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
SCM440 Nitrided has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,416°C (2,581 °F).
Mechanical16
SCM440 Nitrided has a yield strength of 850 MPa (123 ksi) and a tensile strength of 980 MPa (142 ksi) — stronger than 88% of steel grades. Elongation at break is 12% and the elastic modulus is 210 GPa (30.5 Msi).
Thermal6
SCM440 Nitrided is rated for continuous service to 450°C (842 °F). It conducts heat at 42.6 W/m·K (24.6 BTU/hr·ft·°F), worse than 51% of steel grades. Thermal expansion is 12.3 µm/m·K (6.83 µin/in·°F).
Electrical3
SCM440 Nitrided conducts electricity at 7.8 % IACS, worse than 57% of steel grades.
Chemical & Environmental3
Corrosion resistance is poor (20/100), better than 87% of steel grades.
Sustainability4
Producing a kilogram of SCM440 Nitrided takes about 29 MJ of energy and emits 2.1 kg of CO₂ — less than 53% of steel grades. Typical recycled content is 30%.
Manufacturability6
SCM440 Nitrided's machinability is poor (15/100, worse than 98% of steel grades); weldability not recommended (5/100); formability not recommended (3/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with SCM440 Nitrided
Is SCM440 easy to machine?
Machines best at 200–280 HB with coated carbide, ~120–180 m/min turning; above 40 HRC switch to CBN/ceramic or grind.
Can SCM440 be welded?
Weldable with low-hydrogen consumables but requires 250–350 °C preheat, interpass control and immediate PWHT/temper at 600–650 °C to avoid HAZ cracking.
Can SCM440 be formed, bent or molded?
Hot forge at 1100–1200 °C then normalize; cold bending only in the annealed condition with generous radii (≥3t).
What surface finishes work on SCM440?
Not corrosion resistant — use black oxide, phosphate, Zn or Zn-Ni plating, or nitriding; bake 190–220 °C for 4 h after plating parts above ~35 HRC to relieve hydrogen.
SCM440 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 SCM440 | 0.38 – 0.43 | 0.4 |
| 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 |
| Mo | 0.15 – 0.3 | 0.22 |
| Niresidual, max | ≤ 0.25 | |
| Curesidual, max | ≤ 0.3 | |
| Fe | balance |
SCM440 Nitrided — frequently asked
What is SCM440 Nitrided used for?
SCM440 Nitrided is typically used for drive shafts, crankshafts and industrial bolts. In short: workhorse Cr-Mo Japanese bar.
What is the yield strength of SCM440 Nitrided?
SCM440 Nitrided has a typical yield strength of 850 MPa (123 ksi) and a tensile strength of 980 MPa (142 ksi) — stronger than 88% of steel grades. Strength varies by condition: see the 11 listed tempers.
Is SCM440 Nitrided easy to machine?
Not especially — machinability is rated poor (15/100, worse than 98% of steel grades). Machines best at 200–280 HB with coated carbide, ~120–180 m/min turning; above 40 HRC switch to CBN/ceramic or grind.
Can SCM440 Nitrided be welded?
Not readily — weldability is rated not recommended (5/100). Weldable with low-hydrogen consumables but requires 250–350 °C preheat, interpass control and immediate PWHT/temper at 600–650 °C to avoid HAZ cracking.
What surface finishes work on SCM440 Nitrided?
Not corrosion resistant — use black oxide, phosphate, Zn or Zn-Ni plating, or nitriding; bake 190–220 °C for 4 h after plating parts above ~35 HRC to relieve hydrogen.
Can SCM440 Nitrided be formed, bent or molded?
Hot forge at 1100–1200 °C then normalize; cold bending only in the annealed condition with generous radii (≥3t).
What is the maximum service temperature of SCM440 Nitrided?
SCM440 Nitrided is rated for continuous use to about 450°C (842 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between SCM440-HR and SCM440-IH?
HR is the default condition — cheapest stock form for parts that will be machined then heat treated by the fabricator. IH: for journals, splines and guideways needing a wear-resistant 52–58 HRC case over a tough Q&T core. Yield strength is 590 MPa in HR versus 880 MPa in IH.
Can FabDigit make parts in SCM440 Nitrided?
Yes — SCM440 Nitrided 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 structural steels for machine structural use — JSA (2016)
- GB/T 3077 — Alloy structural steels (42CrMo) — SAC (2015)
- ASTM A29/A29M & A322 (AISI 4140) — ASTM (2020)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels — ASM International (1990)
- ASM Handbook Vol.19 — Fatigue and Fracture — ASM International (1996)
- 42CrMo4 / 4140 heat-treatable steel datasheet — Böhler / Ovako (2022)
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.