Steel SNCM431-QT (Quenched and tempered)
Heat-treated state · default condition
JIS SNCM431
Use the common delivery state, oil quenched at 820–870 °C and tempered at 570–670 °C to the 830 MPa class, for shafts, gear blanks and rods needing strength with 20% elongation.
Values for the QT condition
Other SNCM431 tempers and conditions
SNCM431 is listed in 9 conditions; see the grade overview at SNCM431.
Compare all 9 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Solution annealed | Pick the full anneal at 820–860 °C with furnace cooling for post-forging softening, heavy machining or as stock before re-hardening, giving the lowest 200 HB and best machinability. | 470 | 690 | 23 | 200 HB | — |
Hot rolled | Choose as-rolled bar as the lowest-cost delivery form for blanks that will be quenched and tempered or forged later; properties scatter around 520 MPa yield and 235 HB. | 520 | 800 | 19 | 21 HRC | 8 % IACS |
Normalized | Use normalizing at 870–900 °C with air cooling to refine and homogenize forged structure as an intermediate or delivery state, stronger than annealed at 570 MPa yield yet still machinable. | 570 | 850 | 20 | 24 HRC | — |
Cold drawn | Pick annealed and cold-drawn bar for accurate small diameters and bright surface ready for direct machining, accepting 12% elongation and residual stress from drawing. | 650 | 780 | 12 | 20 HRC | 8 % IACS |
Stress relieved | Apply stress relief at 550–650 °C after welding or rough machining to stabilize dimensions while keeping essentially quench-and-temper hardness at 265 HB. | 730 | 880 | 20 | 26 HRC | 7.8 % IACS |
QTDefaultThis page Quenched and tempered | Use the common delivery state, oil quenched at 820–870 °C and tempered at 570–670 °C to the 830 MPa class, for shafts, gear blanks and rods needing strength with 20% elongation. | 760 | 900 | 20 | 28 HRC | — |
tempered ~590–620 °C | Choose the 28–32 HRC temper at 590–620 °C as the general medium-strength setting for mid-section drive shafts, balancing 850 MPa yield, 18% elongation and machinability. | 850 | 990 | 18 | 30 HRC | — |
tempered ~540–580 °C | Pick tempering at 540–580 °C to 32–36 HRC for shafts and fasteners under higher contact or bending stress; yield reaches 980 MPa with slightly reduced impact toughness. | 980 | 1,110 | 16 | 34 HRC | — |
tempered ~480–520 °C | Use the 480–520 °C temper to 36–40 HRC for small high-strength parts such as pins and high-tensile bolts; toughness and machinability drop and hydrogen embrittlement must be controlled. | 1,120 | 1,250 | 13 | 38 HRC | — |
What is SNCM431-QT?
SNCM431-QT is SNCM431 heat treated to QT — use the common delivery state, oil quenched at 820–870 °C and tempered at 570–670 °C to the 830 MPa class, for shafts, gear blanks and rods needing strength with 20% elongation. SNCM431-QT has a yield strength of 760 MPa (110 ksi) and a tensile strength of 900 MPa (131 ksi) — stronger than 85% of steel grades. Elongation at break is 20% and the elastic modulus is 205 GPa (29.7 Msi). SNCM431-QT 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).
Advantages
- High strength — 760 MPa (110 ksi), better than 85% of steel grades
SNCM431-QT properties
Typical room-temperature values for SNCM431-QT; 14 are specific to this condition. Other listed values are SNCM431 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
SNCM431-QT 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
SNCM431-QT has a yield strength of 760 MPa (110 ksi) and a tensile strength of 900 MPa (131 ksi) — stronger than 85% of steel grades. Elongation at break is 20% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
SNCM431-QT 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 12.3 µm/m·K (6.83 µin/in·°F).
Electrical3
SNCM431-QT 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 SNCM431-QT takes about 30 MJ of energy and emits 2.3 kg of CO₂ — more than 56% of steel grades. Typical recycled content is 30%.
Manufacturability7
SNCM431-QT's machinability is fair (50/100, worse than 53% of steel grades); weldability fair (40/100); formability poor (30/100).
Common Calculations5
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with SNCM431-QT
Is SNCM431 easy to machine?
Annealed and normalized material machines most easily (about 55-65% of AISI 1212). Above 30 HRC after quench and temper, use coated carbide with lower speed, higher feed and generous coolant.
Can SNCM431 be welded?
Carbon equivalent is about 0.7-0.8, so use 200-300 °C preheat and low-hydrogen consumables, followed by a 580-650 °C temper to avoid martensitic cracking.
Can SNCM431 be formed, bent or molded?
Forge at approximately 1100-1200 °C with finishing temperature no lower than 850 °C. Cold forming is restricted to light bending and upsetting in the annealed condition.
What surface finishes work on SNCM431?
No inherent corrosion resistance — apply black oxide, phosphate, zinc or chrome plating, or paint. Electroplated parts in the high-strength tempers require hydrogen bake-out at 190-210 °C for 4-24 h.
SNCM431 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 | 0.27 – 0.35 | 0.31 |
| 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 | — |
SNCM431-QT — frequently asked
What is SNCM431-QT used for?
SNCM431-QT is typically used for shafts, structural bolts and pressure vessel components. In short: balanced strength and toughness; through-hardening Ni-Cr-Mo bar; weldable with preheat.
What is the yield strength of SNCM431-QT?
SNCM431-QT has a typical yield strength of 760 MPa (110 ksi) and a tensile strength of 900 MPa (131 ksi) — stronger than 85% of steel grades. Strength varies by condition: see the 9 listed tempers.
Is SNCM431-QT easy to machine?
Reasonably — machinability is rated fair (50/100, worse than 53% of steel grades). Annealed and normalized material machines most easily (about 55-65% of AISI 1212). Above 30 HRC after quench and temper, use coated carbide with lower speed, higher feed and generous coolant.
Can SNCM431-QT be welded?
With care — weldability is rated fair (40/100). Carbon equivalent is about 0.7-0.8, so use 200-300 °C preheat and low-hydrogen consumables, followed by a 580-650 °C temper to avoid martensitic cracking.
What surface finishes work on SNCM431-QT?
No inherent corrosion resistance — apply black oxide, phosphate, zinc or chrome plating, or paint. Electroplated parts in the high-strength tempers require hydrogen bake-out at 190-210 °C for 4-24 h.
Can SNCM431-QT be formed, bent or molded?
Forge at approximately 1100-1200 °C with finishing temperature no lower than 850 °C. Cold forming is restricted to light bending and upsetting in the annealed condition.
What is the maximum service temperature of SNCM431-QT?
SNCM431-QT 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 SNCM431-QT and SNCM431-A?
QT is the default condition — use the common delivery state, oil quenched at 820–870 °C and tempered at 570–670 °C to the 830 MPa class, for shafts, gear blanks and rods needing strength with 20% elongation. A: pick the full anneal at 820–860 °C with furnace cooling for post-forging softening, heavy machining or as stock before re-hardening, giving the lowest 200 HB and best machinability. Yield strength is 760 MPa in QT versus 470 MPa in A.
Sources
- SAE J404 Chemical Compositions of SAE Alloy Steels (8630) — SAE International (2021)
- ASM Handbook Vol.1: Properties and Selection — Irons, Steels, and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol.19: Fatigue and Fracture — ASM International (1996)
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.