Steel SNCM439 · supply condition
Steel SNCM439-CD
Properties of the CD condition, compared with the other SNCM439 tempers.
Pick for close-tolerance bright bar used directly on lathes/screw machines without further heat treatment.
What is SNCM439-CD?
SNCM439-CD is SNCM439 supplied in the CD condition — pick for close-tolerance bright bar used directly on lathes/screw machines without further heat treatment. SNCM439-CD has a yield strength of 850 MPa (123 ksi) and a tensile strength of 1,000 MPa (145 ksi) — stronger than 88% of steel grades. Elongation at break is 10% and the elastic modulus is 205 GPa (29.7 Msi). SNCM439-CD has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,420°C (2,588 °F). HR is the default condition FabDigit quotes; CD is available on request or by drawing note.
Advantages
- High strength — 850 MPa (123 ksi), better than 88% of steel grades
- Polishes to a fine finish — 70/100, better than 87% of steel grades
Limitations
- Limited ductility — 10%, worse than 91% of steel grades
- Limited formability — 20/100, worse than 80% of steel grades
SNCM439-CD properties
Typical room-temperature values for SNCM439-CD — 11 properties are specific to this condition; the rest are grade-level values shared by every SNCM439 temper. Each bar shows where the value sits among the steel grades in FabDigit's library — further right is higher.
Physical3
SNCM439-CD has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,420°C (2,588 °F).
Mechanical16
SNCM439-CD has a yield strength of 850 MPa (123 ksi) and a tensile strength of 1,000 MPa (145 ksi) — stronger than 88% of steel grades. Elongation at break is 10% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
SNCM439-CD 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 12.3 µm/m·K (6.83 µin/in·°F).
Electrical3
SNCM439-CD conducts electricity at 7 % IACS, worse than 74% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of SNCM439-CD takes about 30 MJ of energy and emits 2.3 kg of CO₂ — more than 55% of steel grades. Typical recycled content is 30%.
Manufacturability6
SNCM439-CD's machinability is fair (52/100, better than 52% of steel grades); weldability fair (35/100); formability poor (20/100).
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Other SNCM439 tempers and conditions
SNCM439 is also supplied in 12 other conditions. The full side-by-side table is on the SNCM439 overview.
- HRDefaultStandard mill-stock condition for bars and forging feedstock that the user will heat treat later.620 MPa yield · 26 HRC
- Q&T 50-54 HRCMaximum-strength/wear condition (≈1900 MPa); brittle and notch-sensitive — grind only, avoid sharp corners.1,620 MPa yield · 52 HRC
- Q&T 45-49 HRCHigh-strength aerospace/landing-gear class level; needs careful grinding and hydrogen-relief baking after plating.1,500 MPa yield · 47 HRC
- Q&T 40-44 HRCUse when wear and high yield are needed and impact loading is moderate; machining becomes difficult.1,300 MPa yield · 42 HRC
- Q&T 36-40 HRCHigher strength for medium-section shafts and tooling holders where machining is still required.1,150 MPa yield · 38 HRC
- Q&T 32-36 HRCCommon general-purpose strength/toughness balance for gear shafts and heavy fasteners.1,000 MPa yield · 34 HRC
- Q&TStandard delivery condition for shafts and highly loaded parts; JIS spec minima 985 MPa UTS / 885 MPa YS.950 MPa yield · 34 HRC
- NitridedChoose for wear-resistant, fatigue-strong shaft journals and spindles with a tough Q&T core and minimal distortion.950 MPa yield · 34 HRC
- Q&T 28-32 HRCToughest practical Q&T level — best for impact-loaded shafts, connecting rods and parts to be welded or nitrided.870 MPa yield · 30 HRC
- NormalizedUniform fine-grain structure for forgings before Q&T; already quite strong but low toughness for a Ni-Cr-Mo steel.860 MPa yield · 39 HRC
- CDPick for close-tolerance bright bar used directly on lathes/screw machines without further heat treatment.850 MPa yield · 30 HRC
- CRChoose for thin strip/sheet with good surface and tighter thickness before heat treatment.760 MPa yield · 29 HRC
- AnnealedSoftest condition — use for heavy machining, deep boring or cold forming before final Q&T.470 MPa yield · 217 HB
Working with SNCM439-CD
Is SNCM439 easy to machine?
Machine in the annealed or ≤32 HRC condition with rigid setups, carbide tooling and generous coolant; above 40 HRC switch to CBN turning or grinding.
Can SNCM439 be welded?
Weldable only with care — preheat 250–350 °C, low-hydrogen filler, interpass control and immediate post-weld temper below the last tempering temperature; avoid welding in high-strength tempers.
Can SNCM439 be formed, bent or molded?
Cold forming limited to the annealed condition; hot forge 1150–1200 °C, finish above 900 °C and slow-cool/normalize before machining and Q&T.
What surface finishes work on SNCM439?
Takes phosphate, black oxide, hard chrome, zinc or cadmium plating and paint well; bake at 190–220 °C after plating to relieve hydrogen, and nitride or QPQ for wear surfaces.
SNCM439 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 | 0.36 – 0.43 | 0.4 |
| Si | 0.15 – 0.35 | 0.25 |
| Mn | 0.6 – 0.9 | 0.75 |
| P | ≤ 0.03 | — |
| S | ≤ 0.03 | — |
| Ni | 1.6 – 2 | 1.8 |
| Cr | 0.6 – 1 | 0.8 |
| Mo | 0.15 – 0.3 | 0.22 |
| Curesidual max | ≤ 0.3 | — |
| Fe | balance | — |
SNCM439-CD — frequently asked
What is SNCM439-CD used for?
SNCM439-CD is typically used for heavy-section drive shafts, gear shafts and pinions, connecting rods, high-strength bolts and studs, mould bases and die holders and aerospace fittings. In short: workhorse Ni-Cr-Mo bar.
What is the yield strength of SNCM439-CD?
SNCM439-CD has a typical yield strength of 850 MPa (123 ksi) and a tensile strength of 1,000 MPa (145 ksi) — stronger than 88% of steel grades. Strength varies by condition: see the 13 listed tempers.
Is SNCM439-CD easy to machine?
Reasonably — machinability is rated fair (52/100, better than 52% of steel grades). Machine in the annealed or ≤32 HRC condition with rigid setups, carbide tooling and generous coolant; above 40 HRC switch to CBN turning or grinding.
Can SNCM439-CD be welded?
With care — weldability is rated fair (35/100). Weldable only with care — preheat 250–350 °C, low-hydrogen filler, interpass control and immediate post-weld temper below the last tempering temperature; avoid welding in high-strength tempers.
What surface finishes work on SNCM439-CD?
Takes phosphate, black oxide, hard chrome, zinc or cadmium plating and paint well; bake at 190–220 °C after plating to relieve hydrogen, and nitride or QPQ for wear surfaces.
Can SNCM439-CD be formed, bent or molded?
Cold forming limited to the annealed condition; hot forge 1150–1200 °C, finish above 900 °C and slow-cool/normalize before machining and Q&T.
What is the maximum service temperature of SNCM439-CD?
SNCM439-CD 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 SNCM439-HR and SNCM439-CD?
HR is the default condition — standard mill-stock condition for bars and forging feedstock that the user will heat treat later. CD: pick for close-tolerance bright bar used directly on lathes/screw machines without further heat treatment. Yield strength is 620 MPa in HR versus 850 MPa in CD.
Can FabDigit make parts in SNCM439-CD?
Yes — SNCM439-CD 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)
- GB/T 3077 (40CrNiMoA) — SAC (2015)
- SAE J404 / ASTM A29 (4340) — SAE / ASTM (2020)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels — ASM International (1990)
- ASM Handbook Vol.19 — Fatigue and Fracture — ASM International (1996)
- MMPDS-16 (4340 typical properties) — Battelle/FAA (2021)
- Machinery's Handbook, machinability ratings — Industrial Press (2020)
- Mysteel / SMM (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.