Steel SNC836 QT-HH
Hardness band
JIS SNC836
QT-HH = q&T 302–352 HB
Higher-strength Q&T level (≈1100 MPa) for heavily loaded shafts and gear blanks where some toughness can be traded for strength.
Values for the QT-HH condition
Other SNC836 tempers and conditions
SNC836 is listed in 8 conditions; see the grade overview at SNC836.
Compare all 8 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Solution annealed | Softest condition, chosen for heavy machining, deep hole drilling or cold straightening before final hardening. | 460 | 720 | 22 | 210 HB | — |
Normalized | Grain refining / stress-relief condition for forgings before final Q&T, or for moderately loaded parts. | 580 | 880 | 18 | 26 HRC | 6 % IACS |
Hot rolled | Mill supply condition for stock that will be re-heat-treated; already fairly hard because the steel air-hardens. | 600 | 950 | 15 | 28 HRC | 6 % IACS |
Cold drawn | Bright bar for close-tolerance shafts and studs used without further heat treatment. | 760 | 900 | 11 | 26 HRC | 6 % IACS |
QTDefault Quenched and tempered | Standard JIS delivery condition for gears, shafts and heavy bolts — 930 MPa minimum tensile with good toughness through large sections. | 850 | 990 | 18 | 31 HRC | — |
Carburized and hardened | Pick when the tooth flank or journal must resist wear and contact fatigue while the high-Ni core stays tough at ~1000 MPa. | 850 | 1,050 | 12 | 60 HRC | 6 % IACS |
Nitrided | Low-distortion surface hardening for finish-machined gears and shafts that must keep tight Q&T core geometry. | 850 | 990 | 16 | 57 HRC | 6 % IACS |
QT-HHThis page Q&T 302–352 HB | Higher-strength Q&T level (≈1100 MPa) for heavily loaded shafts and gear blanks where some toughness can be traded for strength. | 980 | 1,130 | 14 | 35 HRC | — |
What is SNC836 QT-HH?
SNC836 QT-HH is SNC836 heat treated to QT-HH — higher-strength Q&T level (≈1100 MPa) for heavily loaded shafts and gear blanks where some toughness can be traded for strength. SNC836 QT-HH has a yield strength of 980 MPa (142 ksi) and a tensile strength of 1,130 MPa (164 ksi) — stronger than 91% of steel grades. Elongation at break is 14% and the elastic modulus is 205 GPa (29.7 Msi). SNC836 QT-HH 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). QT is the default condition FabDigit quotes; QT-HH is available on request or by drawing note.
Advantages
- High strength — 980 MPa (142 ksi), better than 91% of steel grades
- Polishes to a fine finish — 70/100, better than 87% of steel grades
Limitations
- Difficult to machine — 34/100, worse than 86% of steel grades
- High embodied carbon — 2.5 kg CO₂/kg, worse than 82% of steel grades
- Poor heat conductor — 33 W/m·K (19.1 BTU/hr·ft·°F), worse than 80% of steel grades
- Low electrical conductivity — 6 % IACS, worse than 78% of steel grades
- Limited ductility — 14%, worse than 75% of steel grades
SNC836 QT-HH properties
Typical room-temperature values for SNC836 QT-HH; 10 are specific to this condition. Other listed values are SNC836 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
SNC836 QT-HH 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
SNC836 QT-HH has a yield strength of 980 MPa (142 ksi) and a tensile strength of 1,130 MPa (164 ksi) — stronger than 91% of steel grades. Elongation at break is 14% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
SNC836 QT-HH is rated for continuous service to 400°C (752 °F). It conducts heat at 33 W/m·K (19.1 BTU/hr·ft·°F), worse than 80% of steel grades. Thermal expansion is 12 µm/m·K (6.67 µin/in·°F).
Electrical3
SNC836 QT-HH conducts electricity at 6 % IACS, worse than 78% of steel grades.
Chemical & Environmental2
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of SNC836 QT-HH takes about 33 MJ of energy and emits 2.5 kg of CO₂ — more than 76% of steel grades. Typical recycled content is 30%.
Manufacturability7
SNC836 QT-HH's machinability is poor (34/100, worse than 86% of steel grades); weldability poor (28/100); formability poor (25/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with SNC836 QT-HH
Is SNC836 easy to machine?
Machine in the annealed or 269–321 HB Q&T state with rigid setups, coated carbide, 60–110 m/min and generous feed; the work-hardening Ni-Cr matrix rubs and glazes at low feeds, so avoid dwelling and finish-grind after case hardening.
Can SNC836 be welded?
Poor weldability (carbon equivalent ~0.9): preheat 250–350 °C, use low-hydrogen electrodes or matching Ni-Cr filler, keep interpass temperature and temper/stress-relieve at 550–620 °C immediately after welding.
Can SNC836 be formed, bent or molded?
Hot forge 1150–1200 °C, finish above 900 °C and cool slowly or normalize; cold forming is limited to straightening — bend only in the annealed condition with generous radii.
What surface finishes work on SNC836?
No corrosion resistance of its own — protect with oil, black oxide, manganese phosphate, zinc or hard-chrome plating; polishes and grinds to a fine finish, but bake after plating to avoid hydrogen embrittlement at ≥1000 MPa.
SNC836 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 |
|---|---|---|
| C | 0.32 – 0.4 | 0.36 |
| Si | 0.15 – 0.35 | 0.25 |
| Mn | 0.35 – 0.65 | 0.5 |
| P | ≤ 0.03 | — |
| S | ≤ 0.03 | — |
| Ni | 3 – 3.5 | 3.25 |
| Cr | 0.6 – 1 | 0.8 |
| Curesidual max | ≤ 0.3 | — |
| Fe | balance | — |
SNC836 QT-HH — frequently asked
What is SNC836 QT-HH used for?
SNC836 QT-HH is typically used for large industrial gears, heavy drive and pinion shafts, gearbox output shafts, crankshafts and connecting rods, nitrided wear shafts and sleeves and high-load couplings. In short: highest core strength in family; nitridable Ni-Cr grade; 400 °C service ceiling.
What is the yield strength of SNC836 QT-HH?
SNC836 QT-HH has a typical yield strength of 980 MPa (142 ksi) and a tensile strength of 1,130 MPa (164 ksi) — stronger than 91% of steel grades. Strength varies by condition: see the 8 listed tempers.
Is SNC836 QT-HH easy to machine?
Not especially — machinability is rated poor (34/100, worse than 86% of steel grades). Machine in the annealed or 269–321 HB Q&T state with rigid setups, coated carbide, 60–110 m/min and generous feed; the work-hardening Ni-Cr matrix rubs and glazes at low feeds, so avoid dwelling and finish-grind after case hardening.
Can SNC836 QT-HH be welded?
Not readily — weldability is rated poor (28/100). Poor weldability (carbon equivalent ~0.9): preheat 250–350 °C, use low-hydrogen electrodes or matching Ni-Cr filler, keep interpass temperature and temper/stress-relieve at 550–620 °C immediately after welding.
What surface finishes work on SNC836 QT-HH?
No corrosion resistance of its own — protect with oil, black oxide, manganese phosphate, zinc or hard-chrome plating; polishes and grinds to a fine finish, but bake after plating to avoid hydrogen embrittlement at ≥1000 MPa.
Can SNC836 QT-HH be formed, bent or molded?
Hot forge 1150–1200 °C, finish above 900 °C and cool slowly or normalize; cold forming is limited to straightening — bend only in the annealed condition with generous radii.
What is the maximum service temperature of SNC836 QT-HH?
SNC836 QT-HH 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 SNC836-QT and SNC836-A?
QT is the default condition — standard JIS delivery condition for gears, shafts and heavy bolts — 930 MPa minimum tensile with good toughness through large sections. A: softest condition, chosen for heavy machining, deep hole drilling or cold straightening before final hardening. Yield strength is 850 MPa in QT versus 460 MPa in A.
Sources
- JIS G 4102 — Nickel chromium steels — Japanese Standards Association (2020)
- ASM Handbook Vol. 1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol. 4 — Heat Treating — ASM International (1991)
- Special steel bar grade data (Ni-Cr structural steels) — Daido Steel / Sanyo Special Steel (2022)
- JIS/GB cross-reference of alloy structural steels (SNC836 ≈ 37CrNi3) — GB/T 3077 reference tables (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.