Steel 817M40 Normalized
Heat-treated state
BS 817M40 · AISI/SAE 4340
Grain-refining condition for forgings prior to hardening; not usually a delivery condition for finished parts.
Values for the Normalized condition
Other 817M40 tempers and conditions
817M40 is listed in 10 conditions; see the grade overview at 817M40.
Compare all 10 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
softened for machining/forming (max 248 HB) | Pick for heavy machining, deep-hole drilling or cold work before final quench and temper. | 470 | 745 | 22 | 217 HB | — |
Condition R | Lowest Q&T level; choose when maximum toughness and easy machining matter more than strength. | 600 | 775 | 20 | 20 HRC | — |
Condition S | General shafting condition with a good strength/toughness balance in large sections. | 660 | 850 | 18 | 25 HRC | — |
TDefault Condition T | The standard stocked En24T bar: strong, tough and still machinable — the default for shafts, gears and studs. | 760 | 930 | 16 | 29 HRC | — |
NormalizedThis page air cooled from ~870 °C | Grain-refining condition for forgings prior to hardening; not usually a delivery condition for finished parts. | 860 | 1,280 | 12 | 39 HRC | 7 % IACS |
Condition V | High-strength shaft/gear condition; machining now needs carbide tooling. | 900 | 1,075 | 14 | 34 HRC | — |
Solution heat treated (unstable) | For highly stressed bolts, torsion bars and drive components in moderate sections. | 1,000 | 1,150 | 13 | 37 HRC | — |
Condition X | Aerospace/motorsport strength level; grind rather than turn, and control hydrogen during plating. | 1,080 | 1,225 | 12 | 40 HRC | — |
Condition Y | Very high strength for compact highly loaded parts; toughness and notch tolerance are markedly reduced. | 1,150 | 1,300 | 11 | 42 HRC | — |
Condition Z | Maximum-strength condition (low-temperature temper) for landing gear and torsion members; brittle and highly hydrogen-sensitive. | 1,400 | 1,650 | 8 | 49 HRC | — |
What is 817M40 Normalized?
817M40 Normalized is 817M40 heat treated to Normalized — grain-refining condition for forgings prior to hardening; not usually a delivery condition for finished parts. 817M40 Normalized has a yield strength of 860 MPa (125 ksi) and a tensile strength of 1,280 MPa (186 ksi) — stronger than 89% of steel grades. Elongation at break is 12% and the elastic modulus is 205 GPa (29.7 Msi). 817M40 Normalized 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). T is the default condition FabDigit quotes; Normalized is available on request or by drawing note.
Advantages
- High strength — 860 MPa (125 ksi), better than 89% of steel grades
- Polishes to a fine finish — 68/100, better than 83% of steel grades
Limitations
- Limited formability — 14/100, worse than 90% of steel grades
- Low fracture toughness — 48 MPa·√m (43.7 ksi·√in), worse than 88% of steel grades
- Difficult to machine — 32/100, worse than 87% of steel grades
- Limited ductility — 12%, worse than 84% of steel grades
- Difficult to weld — 25/100, worse than 77% of steel grades
817M40 Normalized properties
Typical room-temperature values for 817M40 Normalized; 22 are specific to this condition. Other listed values are 817M40 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
817M40 Normalized 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
817M40 Normalized has a yield strength of 860 MPa (125 ksi) and a tensile strength of 1,280 MPa (186 ksi) — stronger than 89% of steel grades. Elongation at break is 12% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
817M40 Normalized 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
817M40 Normalized 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 817M40 Normalized takes about 33 MJ of energy and emits 2.3 kg of CO₂ — more than 76% of steel grades. Typical recycled content is 35%.
Manufacturability7
817M40 Normalized's machinability is poor (32/100, worse than 87% of steel grades); weldability poor (25/100); formability not recommended (14/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 817M40 Normalized
Is 817M40 easy to machine?
Machine in the annealed or T condition with rigid setups and carbide tooling; above ~350 HB switch to grinding, and allow stock for distortion if heat treating after rough machining.
Can 817M40 be welded?
Weldable only with care — preheat 250–350 °C, low-hydrogen consumables, and immediate post-weld temper below the original tempering temperature to avoid hard, crack-prone HAZ.
Can 817M40 be formed, bent or molded?
Hot forge at 1050–1200 °C then normalize; cold forming and bending are limited to the annealed condition with generous radii.
What surface finishes work on 817M40?
No anodizing — protect with zinc/zinc-nickel or hard chrome plating (bake 190 °C after plating to relieve hydrogen), black oxide, phosphate, paint, or gas nitride for wear surfaces.
817M40 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 | 0.36 – 0.44 | 0.4 |
| Si | 0.1 – 0.35 | 0.25 |
| Mn | 0.45 – 0.7 | 0.6 |
| Ni | 1.3 – 1.7 | 1.5 |
| Cr | 1 – 1.4 | 1.2 |
| Mo | 0.2 – 0.35 | 0.28 |
| S0.015–0.040 for free-machining 817M40 variants | ≤ 0.04 | 0.02 |
| P | ≤ 0.04 | 0.02 |
| Fe | balance | — |
817M40 Normalized — frequently asked
What is 817M40 Normalized used for?
817M40 Normalized is typically used for aircraft landing gear, high-strength shafts, gears and fasteners. In short: deep-hardening 4340 equivalent; high strength with toughness; needs preheat to weld.
What is the yield strength of 817M40 Normalized?
817M40 Normalized has a typical yield strength of 860 MPa (125 ksi) and a tensile strength of 1,280 MPa (186 ksi) — stronger than 89% of steel grades. Strength varies by condition: see the 10 listed tempers.
Is 817M40 Normalized easy to machine?
Not especially — machinability is rated poor (32/100, worse than 87% of steel grades). Machine in the annealed or T condition with rigid setups and carbide tooling; above ~350 HB switch to grinding, and allow stock for distortion if heat treating after rough machining.
Can 817M40 Normalized be welded?
Not readily — weldability is rated poor (25/100). Weldable only with care — preheat 250–350 °C, low-hydrogen consumables, and immediate post-weld temper below the original tempering temperature to avoid hard, crack-prone HAZ.
What surface finishes work on 817M40 Normalized?
No anodizing — protect with zinc/zinc-nickel or hard chrome plating (bake 190 °C after plating to relieve hydrogen), black oxide, phosphate, paint, or gas nitride for wear surfaces.
Can 817M40 Normalized be formed, bent or molded?
Hot forge at 1050–1200 °C then normalize; cold forming and bending are limited to the annealed condition with generous radii.
What is the maximum service temperature of 817M40 Normalized?
817M40 Normalized 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 817M40-T and 817M40-Z?
T is the default condition — the standard stocked En24T bar: strong, tough and still machinable — the default for shafts, gears and studs. Z: maximum-strength condition (low-temperature temper) for landing gear and torsion members; brittle and highly hydrogen-sensitive. Yield strength is 760 MPa in T versus 1,400 MPa in Z.
Sources
- BS 970-1:1991 / BS 970 Part 3 — Wrought steels for mechanical and allied engineering purposes (817M40) — BSI (1991)
- ASTM A29/A29M and SAE J404 (AISI 4340 equivalent) — ASTM / SAE (2020)
- GB/T 3077 — (40CrNiMoA) — SAC (2015)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol.19 — Fatigue and Fracture (4340 K_IC and S-N data) — ASM International (1996)
- MMPDS-17 low-alloy steel allowables (4340) — Battelle/FAA (2022)
- En24 / 817M40 alloy steel bar datasheets — West Yorkshire Steel / Interlloy (2023)
- 40CrNiMo — Mysteel / 1688 (2026)
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.