Steel SNCM630-HR (Hot rolled)
Supply condition
JIS SNCM630
Cheapest stock form for parts that will be fully heat treated after rough machining.
Values for the HR condition
Other SNCM630 tempers and conditions
SNCM630 is listed in 11 conditions; see the grade overview at SNCM630.
Compare all 11 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Solution annealed | Pick for deep machining, cold sawing or before final quench-and-temper. | 640 | 850 | 20 | 24 HRC | — |
HRThis page Hot rolled | Cheapest stock form for parts that will be fully heat treated after rough machining. | 700 | 980 | 16 | 29 HRC | 5.8 % IACS |
Normalized | Pick for uniform grain and moderate strength on large forgings before final heat treatment. | 780 | 1,030 | 17 | 31 HRC | — |
Cold drawn | Pick for close-tolerance small-diameter bar where a bright finish is needed before final heat treatment. | 800 | 950 | 12 | 28 HRC | 5.7 % IACS |
high-temperature temper | Pick when maximum toughness and machinability are wanted in a heat-treated part. | 910 | 1,030 | 18 | 32 HRC | — |
QT-HDefault Q&T per JIS G4103 | Standard commercial supply condition: ≥1080 MPa tensile with good toughness for shafts and high-load fasteners. | 1,000 | 1,150 | 17 | 34 HRC | — |
Q&T then gas/plasma nitrided | Pick when a Q&T core must carry load while the surface needs wear and fatigue resistance without distortion. | 1,000 | 1,150 | 14 | 34 HRC | 5.5 % IACS |
Q&T 34–38 HRC | Balanced strength/toughness condition for gear shafts and heavily loaded machine parts. | 1,050 | 1,170 | 16 | 36 HRC | — |
Q&T 38–42 HRC | Pick for high-strength airframe/landing-gear-type parts where some toughness is still required. | 1,180 | 1,300 | 13 | 40 HRC | — |
low-temperature temper | Pick for maximum strength shafts, tool holders and dies; grind after treatment. | 1,330 | 1,450 | 11 | 44 HRC | — |
near as-quenched strength | Only for wear-critical, low-toughness-demand parts; notch and hydrogen sensitivity are high. | 1,450 | 1,600 | 9 | 48 HRC | — |
What is SNCM630-HR?
SNCM630-HR is SNCM630 supplied in the HR condition — cheapest stock form for parts that will be fully heat treated after rough machining. SNCM630-HR has a yield strength of 700 MPa (102 ksi) and a tensile strength of 980 MPa (142 ksi) — stronger than 81% of steel grades. Elongation at break is 16% and the elastic modulus is 205 GPa (29.7 Msi). SNCM630-HR 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-H is the default condition FabDigit quotes; HR is available on request or by drawing note.
Advantages
- Polishes to a fine finish — 72/100, better than 92% of steel grades
- High strength — 700 MPa (102 ksi), better than 81% of steel grades
Limitations
- High embodied carbon — 2.5 kg CO₂/kg, worse than 82% of steel grades
- Low electrical conductivity — 5.8 % IACS, worse than 79% of steel grades
SNCM630-HR properties
Typical room-temperature values for SNCM630-HR; 22 are specific to this condition. Other listed values are SNCM630 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
SNCM630-HR 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
SNCM630-HR has a yield strength of 700 MPa (102 ksi) and a tensile strength of 980 MPa (142 ksi) — stronger than 81% of steel grades. Elongation at break is 16% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
SNCM630-HR is rated for continuous service to 400°C (752 °F). It conducts heat at 38 W/m·K (22 BTU/hr·ft·°F), worse than 69% of steel grades. Thermal expansion is 12.3 µm/m·K (6.83 µin/in·°F).
Electrical3
SNCM630-HR conducts electricity at 5.8 % IACS, worse than 79% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (13/100), better than 66% of steel grades.
Sustainability4
Producing a kilogram of SNCM630-HR takes about 34 MJ of energy and emits 2.5 kg of CO₂ — more than 82% of steel grades. Typical recycled content is 30%.
Manufacturability8
SNCM630-HR's machinability is fair (42/100, worse than 73% of steel grades); weldability fair (35/100); formability poor (30/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with SNCM630-HR
Is SNCM630 easy to machine?
Machine in the annealed or ≤34 HRC condition with rigid setups, carbide tooling and 60–120 m/min; above 40 HRC use ceramic/CBN or grinding.
Can SNCM630 be welded?
Poor weldability due to high hardenability — preheat 250–350 °C, low-hydrogen or matching filler, and immediately post-weld temper below the original tempering temperature.
Can SNCM630 be formed, bent or molded?
Hot forge 1150–900 °C then slow cool/anneal; cold forming is impractical above ~250 HB.
What surface finishes work on SNCM630?
Not anodizable; use phosphate + oil, black oxide, zinc or Zn-Ni plating (bake 190 °C ≥4 h to de-embrittle), nitriding or hard chrome for wear.
SNCM630 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 | 0.25 – 0.35 | 0.3 |
| Si | 0.15 – 0.35 | 0.25 |
| Mn | 0.35 – 0.6 | 0.48 |
| P | ≤ 0.03 | — |
| S | ≤ 0.03 | — |
| Ni | 2.5 – 3.5 | 3 |
| Cr | 2.5 – 3.5 | 3 |
| Mo | 0.5 – 0.7 | 0.6 |
| Curesidual max | ≤ 0.3 | — |
| Fe | balance | — |
SNCM630-HR — frequently asked
What is SNCM630-HR used for?
SNCM630-HR is typically used for aircraft landing gear, high-strength bolts and shafts. In short: highest strength in family; 4340-class Ni-Cr-Mo steel; deep-hardening heavy sections.
What is the yield strength of SNCM630-HR?
SNCM630-HR has a typical yield strength of 700 MPa (102 ksi) and a tensile strength of 980 MPa (142 ksi) — stronger than 81% of steel grades. Strength varies by condition: see the 11 listed tempers.
Is SNCM630-HR easy to machine?
Not especially — machinability is rated fair (42/100, worse than 73% of steel grades). Machine in the annealed or ≤34 HRC condition with rigid setups, carbide tooling and 60–120 m/min; above 40 HRC use ceramic/CBN or grinding.
Can SNCM630-HR be welded?
With care — weldability is rated fair (35/100). Poor weldability due to high hardenability — preheat 250–350 °C, low-hydrogen or matching filler, and immediately post-weld temper below the original tempering temperature.
What surface finishes work on SNCM630-HR?
Not anodizable; use phosphate + oil, black oxide, zinc or Zn-Ni plating (bake 190 °C ≥4 h to de-embrittle), nitriding or hard chrome for wear.
Can SNCM630-HR be formed, bent or molded?
Hot forge 1150–900 °C then slow cool/anneal; cold forming is impractical above ~250 HB.
What is the maximum service temperature of SNCM630-HR?
SNCM630-HR 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 SNCM630 QT-H and SNCM630-A?
QT-H is the default condition — standard commercial supply condition: ≥1080 MPa tensile with good toughness for shafts and high-load fasteners. A: pick for deep machining, cold sawing or before final quench-and-temper. Yield strength is 1,000 MPa in QT-H versus 640 MPa in A.
Sources
- JIS G4103 Nickel-chromium-molybdenum steels — JSA (2018)
- 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)
- ASM Handbook Vol.16: Machining — ASM International (1989)
- MMPDS-style typical property data for 4340-class low-alloy steels — Battelle/FAA (2022)
- GB/T 3077 (30Cr2Ni2Mo comparison) — SAC (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.