Steel SCM440 · hardness band
Steel SCM440 Q&T 34-38 HRC
Properties of the Q&T 34-38 HRC condition, compared with the other SCM440 tempers.
Higher-strength shafts, high-tensile bolting and moulds where toughness is still needed.
What is SCM440 Q&T 34-38 HRC?
SCM440 Q&T 34-38 HRC is SCM440 heat treated to Q&T 34-38 HRC — higher-strength shafts, high-tensile bolting and moulds where toughness is still needed. SCM440 Q&T 34-38 HRC has a yield strength of 1,060 MPa (154 ksi) and a tensile strength of 1,180 MPa (171 ksi) — stronger than 93% of steel grades. Elongation at break is 14% and the elastic modulus is 210 GPa (30.5 Msi). SCM440 Q&T 34-38 HRC 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; Q&T 34-38 HRC is available on request or by drawing note.
Advantages
- High strength — 1,060 MPa (154 ksi), better than 93% of steel grades
- Polishes to a fine finish — 65/100, better than 78% of steel grades
Limitations
- Difficult to machine — 40/100, worse than 76% of steel grades
- Limited ductility — 14%, worse than 75% of steel grades
SCM440 Q&T 34-38 HRC properties
Typical room-temperature values for SCM440 Q&T 34-38 HRC — 13 properties are specific to this condition; the rest are grade-level values shared by every SCM440 temper. Each bar shows where the value sits among the steel grades in FabDigit's library — further right is higher.
Physical3
SCM440 Q&T 34-38 HRC 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 Q&T 34-38 HRC has a yield strength of 1,060 MPa (154 ksi) and a tensile strength of 1,180 MPa (171 ksi) — stronger than 93% of steel grades. Elongation at break is 14% and the elastic modulus is 210 GPa (30.5 Msi).
Thermal6
SCM440 Q&T 34-38 HRC is rated for continuous service to 350°C (662 °F). It conducts heat at 42.6 W/m·K (24.6 BTU/hr·ft·°F), better than 50% of steel grades. Thermal expansion is 12.3 µm/m·K (6.83 µin/in·°F).
Electrical3
SCM440 Q&T 34-38 HRC 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 SCM440 Q&T 34-38 HRC 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 Q&T 34-38 HRC's machinability is fair (40/100, worse than 76% of steel grades); weldability fair (40/100); formability fair (35/100).
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Other SCM440 tempers and conditions
SCM440 is also supplied in 10 other conditions. The full side-by-side table is on the SCM440 overview.
- HRDefaultCheapest stock form for parts that will be machined then heat treated by the fabricator.590 MPa yield · 25 HRC
- Q&T 40-45 HRCHighest strength/wear condition for pins, dies and rams; accept low impact toughness and hydrogen-embrittlement risk when plating.1,280 MPa yield · 42 HRC
- Q&T 34-38 HRCHigher-strength shafts, high-tensile bolting and moulds where toughness is still needed.1,060 MPa yield · 36 HRC
- Q&TStandard supply condition for shafts, gears and machine parts needing balanced strength and toughness.880 MPa yield · 30 HRC
- NitridedLow-distortion hard case (~0.2–0.5 mm, 550–650 HV) for wear and fatigue-critical shafts and screws.850 MPa yield · 55 HRC
- CDPick for near-net-size shafts and turned parts needing good surface finish and straightness without further grinding.750 MPa yield · 26 HRC
- Q&T 22-26 HRCMaximum toughness / NACE-friendly hardness cap for pressure and downhole components.720 MPa yield · 24 HRC
- NormalizedUniform fine grain and mid-range strength; used as pre-treatment before machining/hardening or as final state for low-stress parts.655 MPa yield · 32 HRC
- AnnealedChoose for heavy machining, cold forming or deep-hole drilling before final hardening.415 MPa yield · 197 HB
Working with SCM440 Q&T 34-38 HRC
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 Q&T 34-38 HRC — frequently asked
What is SCM440 Q&T 34-38 HRC used for?
SCM440 Q&T 34-38 HRC is typically used for drive shafts, crankshafts and industrial bolts. In short: workhorse Cr-Mo Japanese bar.
What is the yield strength of SCM440 Q&T 34-38 HRC?
SCM440 Q&T 34-38 HRC has a typical yield strength of 1,060 MPa (154 ksi) and a tensile strength of 1,180 MPa (171 ksi) — stronger than 93% of steel grades. Strength varies by condition: see the 11 listed tempers.
Is SCM440 Q&T 34-38 HRC easy to machine?
Not especially — machinability is rated fair (40/100, worse than 76% 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 Q&T 34-38 HRC be welded?
With care — weldability is rated fair (40/100). 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 Q&T 34-38 HRC?
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 Q&T 34-38 HRC 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 Q&T 34-38 HRC?
SCM440 Q&T 34-38 HRC is rated for continuous use to about 350°C (662 °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 Q&T 34-38 HRC?
Yes — SCM440 Q&T 34-38 HRC 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.