Steel En40B
En40B is a BS 970 nitriding steel containing chromium, molybdenum and about 1 % aluminium, cross-referenced to 34CrAlMo5-10 and 38CrMoAl, and stocked annealed, normalized, in conditions T to X, hot rolled or nitrided.
Reference datasheet — En40B is not in the instant-quote catalog. Upload your part and an engineer will quote it in this grade or suggest the closest stocked equivalent.
Values for the T condition
En40B tempers and conditions
En40B is supplied in 8 conditions, soft to hard. T is the default FabDigit quotes; the values on this page are for it.
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 |
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 | — |
Supply forms, finishes and certifications
Ways En40B is supplied — form, process route, surface or paperwork — without a datasheet of their own. The property values above apply.
| Option | What it is | Type |
|---|---|---|
U | Condition U | Coating |
What is En40B?
En40B is a BS 970 nitriding steel containing chromium, molybdenum and about 1 % aluminium, cross-referenced to 34CrAlMo5-10 and 38CrMoAl, and stocked annealed, normalized, in conditions T to X, hot rolled or nitrided. Engineers use it where a very hard, wear-resistant surface is needed with minimal distortion, since nitriding is done at 500–530 °C after final machining: the default quenched and tempered condition gives 745 MPa yield, 930 MPa tensile, 15 % elongation and 277 HB (29 HRC). It is supplied as bar and forgings and cannot be practically welded or cold formed; the aluminium content also complicates plating over the nitrided white layer. Use En39 or En30B when a carburized case is acceptable. En40B 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). En40B has a yield strength of 745 MPa (108 ksi) and a tensile strength of 930 MPa (135 ksi) — stronger than 83% of steel grades. Elongation at break is 15% and the elastic modulus is 210 GPa (30.5 Msi).
What is En40B used for?
- nitrided gears
- spindles
- valve components
Advantages
- High service temperature — 500°C (932 °F), better than 90% of steel grades
- High strength — 745 MPa (108 ksi), better than 83% of steel grades
- Polishes to a fine finish — 65/100, better than 78% of steel grades
Limitations
- Difficult to weld — 20/100, worse than 84% of steel grades
- Limited formability — 20/100, worse than 80% of steel grades
- Poor heat conductor — 34 W/m·K (19.6 BTU/hr·ft·°F), worse than 77% of steel grades
- Low electrical conductivity — 6.6 % IACS, worse than 76% of steel grades
En40B properties
Typical room-temperature values for En40B-T; bars are the position among steel grades.
Physical3
En40B 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 has a yield strength of 745 MPa (108 ksi) and a tensile strength of 930 MPa (135 ksi) — stronger than 83% of steel grades. Elongation at break is 15% and the elastic modulus is 210 GPa (30.5 Msi).
Thermal6
En40B is rated for continuous service to 500°C (932 °F). It conducts heat at 34 W/m·K (19.6 BTU/hr·ft·°F), worse than 77% of steel grades. Thermal expansion is 12 µm/m·K (6.67 µin/in·°F).
Electrical3
En40B conducts electricity at 6.6 % IACS, worse than 76% of steel grades.
Chemical & Environmental3
Corrosion resistance is poor (15/100), better than 75% of steel grades.
Sustainability4
Producing a kilogram of En40B 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's machinability is fair (45/100, worse than 65% of steel grades); weldability poor (20/100); formability poor (20/100).
Common Calculations5
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the steel family
Yield strength against density for every steel grade FabDigit runs. En40B is highlighted; hover a dot for its name, or open the interactive family chart.
Working with En40B
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.
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 |
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.
Surface treatments FabDigit runs on steel parts — pick them in the quote configurator or call them out on the drawing. Each links to its datasheet in the surface-finish library (thickness, specs, call-out, material verdicts).
Organic Coating
Black / Phosphate
Thermal Spray
Equivalent designations
Standards and trade names that resolve to Steel En40B in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- Similar grades
- 34CrAlMo5-1038CrMoAl
How much does En40B cost?
En40B is a budget-cost steel ($), cheaper than about 90% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
En40B — frequently asked
What is En40B used for?
En40B 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?
En40B has a typical yield strength of 745 MPa (108 ksi) and a tensile strength of 930 MPa (135 ksi) — stronger than 83% of steel grades. Strength varies by condition: see the 8 listed tempers.
Is En40B easy to machine?
Reasonably — machinability is rated fair (45/100, worse than 65% 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 be welded?
Not readily — weldability is rated poor (20/100). 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?
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 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?
En40B is rated for continuous use to about 500°C (932 °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.
How much does En40B cost?
En40B is a budget-cost steel ($), cheaper than about 90% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
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; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.