Steel En40B-W
Heat-treated state
W = solution heat treated (unstable)
High-strength core for small sections; tempering temperature approaches the nitriding temperature, so check stability.
Values for the W condition
Other En40B tempers and conditions
En40B is listed in 8 conditions; see the grade overview at En40B.
Compare all 8 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Solution annealed | Pick for heavy roughing, deep-hole drilling or cold sawing before the final quench-and-temper cycle. | 450 | 700 | 20 | 220 HB | — |
Normalized | Bar-stock condition giving uniform grain and machinable hardness before final hardening. | 540 | 800 | 17 | 23 HRC | 6.8 % IACS |
Hot rolled | Raw mill condition sold for re-forging or full heat treatment by the user; properties not guaranteed. | 550 | 850 | 16 | 25 HRC | 6.6 % IACS |
TDefault Condition T | Standard stocked pre-nitriding condition: tough core, ~250–300 HB, machines and then nitrides with minimal distortion. | 745 | 930 | 15 | 29 HRC | 6.6 % IACS |
Q&T + gas/plasma nitrided (case 900–1100 HV) | Final in-service condition: aluminium-nitride case for maximum wear and scuffing resistance with a Condition T/U core. | 745 | 930 | 14 | 68 HRC | — |
Condition V | Use where core strength governs, e.g. heavily loaded pinion shafts, still nitridable. | 880 | 1,080 | 13 | 34 HRC | 6.5 % IACS |
WThis page Solution heat treated (unstable) | High-strength core for small sections; tempering temperature approaches the nitriding temperature, so check stability. | 960 | 1,150 | 12 | 37 HRC | 6.5 % IACS |
Condition X | Maximum commercially supplied core strength; only for small sections and generally not nitrided afterwards. | 1,030 | 1,220 | 11 | 40 HRC | — |
What is En40B-W?
En40B-W is En40B heat treated to W — high-strength core for small sections; tempering temperature approaches the nitriding temperature, so check stability. En40B-W has a yield strength of 960 MPa (139 ksi) and a tensile strength of 1,150 MPa (167 ksi) — stronger than 91% of steel grades. Elongation at break is 12% and the elastic modulus is 210 GPa (30.5 Msi). En40B-W has a density of 7.8 g/cm³ (0.282 lb/in³), lighter than 87% of steel grades. It melts at 1,420°C (2,588 °F). T is the default condition FabDigit quotes; W is available on request or by drawing note.
Advantages
- High strength — 960 MPa (139 ksi), better than 91% of steel grades
- High service temperature — 450°C (842 °F), better than 86% of steel grades
- Polishes to a fine finish — 65/100, better than 78% of steel grades
Limitations
- Limited formability — 8/100, worse than 97% of steel grades
- Difficult to weld — 12/100, worse than 96% of steel grades
- Difficult to machine — 33/100, worse than 86% of steel grades
- Limited ductility — 12%, worse than 84% of steel grades
- Poor heat conductor — 33 W/m·K (19.1 BTU/hr·ft·°F), worse than 80% of steel grades
En40B-W properties
Typical room-temperature values for En40B-W; 22 are specific to this condition. Other listed values are En40B reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
En40B-W has a density of 7.8 g/cm³ (0.282 lb/in³), lighter than 87% of steel grades. It melts at 1,420°C (2,588 °F).
Mechanical16
En40B-W has a yield strength of 960 MPa (139 ksi) and a tensile strength of 1,150 MPa (167 ksi) — stronger than 91% of steel grades. Elongation at break is 12% and the elastic modulus is 210 GPa (30.5 Msi).
Thermal6
En40B-W is rated for continuous service to 450°C (842 °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
En40B-W conducts electricity at 6.5 % IACS, worse than 77% of steel grades.
Chemical & Environmental3
Corrosion resistance is poor (15/100), better than 75% of steel grades.
Sustainability4
Producing a kilogram of En40B-W takes about 31 MJ of energy and emits 2.2 kg of CO₂ — more than 64% of steel grades. Typical recycled content is 25%.
Manufacturability7
En40B-W's machinability is poor (33/100, worse than 86% of steel grades); weldability not recommended (12/100); formability not recommended (8/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with En40B-W
Is En40B easy to machine?
Machine in the Q&T (Condition T/U) state with rigid setups and carbide tooling at ~90–140 m/min; leave 0.05–0.1 mm grinding stock, because after nitriding only grinding or lapping is possible.
Can En40B be welded?
Effectively not weldable for structural joints — high carbon equivalent plus 1 % Al causes cracking and oxide entrapment; if unavoidable, preheat 300–350 °C, use low-hydrogen consumables and temper immediately.
Can En40B be formed, bent or molded?
Hot forge at 1150–850 °C followed by slow cooling and a full anneal; no meaningful cold forming.
What surface finishes work on En40B?
Stress relieve at ~550–650 °C after rough machining, then gas or plasma nitride at 500–530 °C for 0.3–0.7 mm case; oxidise, phosphate or oil for rust protection — do not plate over a white layer without removing it.
En40B 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 | 0.35 – 0.45 | 0.4 |
| Si | 0.1 – 0.45 | 0.25 |
| Mn | 0.45 – 0.7 | 0.55 |
| P | ≤ 0.04 | — |
| S | ≤ 0.04 | — |
| CrGB 38CrMoAl uses 1.35–1.65 | 1.4 – 1.8 | 1.6 |
| Mo | 0.15 – 0.25 | 0.2 |
| Alnitride former; GB 38CrMoAl 0.70–1.10 | 0.9 – 1.3 | 1.1 |
| Niresidual | ≤ 0.4 | — |
| Fe | balance | — |
En40B-W — frequently asked
What is En40B-W used for?
En40B-W is typically used for nitrided gears, spindles and valve components. In short: classic nitriding steel; very hard, low-distortion case; nitrided surface, not weldable.
What is the yield strength of En40B-W?
En40B-W has a typical yield strength of 960 MPa (139 ksi) and a tensile strength of 1,150 MPa (167 ksi) — stronger than 91% of steel grades. Strength varies by condition: see the 8 listed tempers.
Is En40B-W easy to machine?
Not especially — machinability is rated poor (33/100, worse than 86% of steel grades). Machine in the Q&T (Condition T/U) state with rigid setups and carbide tooling at ~90–140 m/min; leave 0.05–0.1 mm grinding stock, because after nitriding only grinding or lapping is possible.
Can En40B-W be welded?
Not readily — weldability is rated not recommended (12/100). Effectively not weldable for structural joints — high carbon equivalent plus 1 % Al causes cracking and oxide entrapment; if unavoidable, preheat 300–350 °C, use low-hydrogen consumables and temper immediately.
What surface finishes work on En40B-W?
Stress relieve at ~550–650 °C after rough machining, then gas or plasma nitride at 500–530 °C for 0.3–0.7 mm case; oxidise, phosphate or oil for rust protection — do not plate over a white layer without removing it.
Can En40B-W be formed, bent or molded?
Hot forge at 1150–850 °C followed by slow cooling and a full anneal; no meaningful cold forming.
What is the maximum service temperature of En40B-W?
En40B-W is rated for continuous use to about 450°C (842 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between En40B-T and En40B-A?
T is the default condition — standard stocked pre-nitriding condition: tough core, ~250–300 HB, machines and then nitrides with minimal distortion. A: pick for heavy roughing, deep-hole drilling or cold sawing before the final quench-and-temper cycle. Yield strength is 745 MPa in T versus 450 MPa in A.
Sources
- BS 970 Part 1 (905M39 / En40B) — Wrought steels for mechanical and allied engineering purposes — BSI (1991)
- GB/T 3077 Alloy Structural Steels (38CrMoAl) — SAC (2015)
- EN 10085 Nitriding steels (34CrAlMo5-10) — CEN (2001)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol.4A — Steel Heat Treating Fundamentals (nitriding) — ASM International (2013)
- Nitriding steel 34CrAlMo5 / 1.8507 data sheet — Böhler / Ovako (2020)
- 38CrMoAl — Mysteel / 1688 (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.