Steel 905M39
BS 905M39
905M39 is a British BS 970 alloy steel, cross-referenced to 9255, supplied annealed, in the T, U, V and W hardened-and-tempered conditions, and quenched, tempered and nitrided.
Reference datasheet — 905M39 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
905M39 tempers and conditions
905M39 is supplied in 5 conditions, soft to hard. T is the default FabDigit quotes; the values on this page are for it.
Compare all 5 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Annealed | Choose for heavy machining or cold work before the customer's own harden-temper-nitride cycle. | 450 | 700 | 20 | 210 HB | — |
TDefault Condition T | Standard stock condition: tough core for general nitrided shafts, spindles, gears and valve components. | 710 | 925 | 15 | 28 HRC | — |
Condition V | Typical core condition specified before nitriding of highly loaded gears, extruder screws and hydraulic rams. | 840 | 1,075 | 13 | 34 HRC | — |
Q&T (cond. V/W) + gas nitrided case | Final in-service condition: 0.3–0.6 mm case at 900–1100 HV over a tough tempered core for wear, scuffing and fatigue resistance. | 840 | 1,075 | 12 | 68 HRC | — |
Solution heat treated (unstable) | Highest routinely supplied core strength — for small sections needing maximum load capacity under the nitride case. | 920 | 1,160 | 12 | 37 HRC | — |
Supply forms, finishes and certifications
Ways 905M39 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 905M39?
905M39 is a British BS 970 alloy steel, cross-referenced to 9255, supplied annealed, in the T, U, V and W hardened-and-tempered conditions, and quenched, tempered and nitrided. It is specified for heavy-duty leaf and coil springs that need high fatigue strength, and its aluminium content (about 1.1 %) gives a strong nitriding response for wear surfaces. Default condition values are 710 MPa yield, 925 MPa tensile, 15 % elongation, 277 HB (28 HRC) and service to 500 °C, with a machinability score of 45. It is not practically weldable; where a weldable Cr-Mo grade is acceptable, use 42CD4. 905M39 has a density of 7.76 g/cm³ (0.28 lb/in³), lighter than 92% of steel grades. It melts at 1,425°C (2,597 °F). 905M39 has a yield strength of 710 MPa (103 ksi) and a tensile strength of 925 MPa (134 ksi) — stronger than 82% of steel grades. Elongation at break is 15% and the elastic modulus is 210 GPa (30.5 Msi).
What is 905M39 used for?
- leaf springs
- coil springs
- stabilizer bars
Advantages
- High service temperature — 500°C (932 °F), better than 90% of steel grades
- Polishes to a fine finish — 70/100, better than 87% of steel grades
- High strength — 710 MPa (103 ksi), better than 82% of steel grades
Limitations
- Difficult to weld — 15/100, worse than 91% of steel grades
- Poor heat conductor — 33 W/m·K (19.1 BTU/hr·ft·°F), worse than 80% of steel grades
- Limited formability — 20/100, worse than 80% of steel grades
905M39 properties
Typical room-temperature values for 905M39-T; bars are the position among steel grades.
Physical3
905M39 has a density of 7.76 g/cm³ (0.28 lb/in³), lighter than 92% of steel grades. It melts at 1,425°C (2,597 °F).
Mechanical16
905M39 has a yield strength of 710 MPa (103 ksi) and a tensile strength of 925 MPa (134 ksi) — stronger than 82% of steel grades. Elongation at break is 15% and the elastic modulus is 210 GPa (30.5 Msi).
Thermal6
905M39 is rated for continuous service to 500°C (932 °F). It conducts heat at 33 W/m·K (19.1 BTU/hr·ft·°F), worse than 80% of steel grades. Thermal expansion is 12.2 µm/m·K (6.78 µin/in·°F).
Electrical3
905M39 conducts electricity at 7 % IACS, worse than 74% of steel grades.
Chemical & Environmental3
Corrosion resistance is poor (16/100), better than 79% of steel grades.
Sustainability4
Producing a kilogram of 905M39 takes about 31 MJ of energy and emits 2.3 kg of CO₂ — more than 64% of steel grades. Typical recycled content is 30%.
Manufacturability7
905M39's machinability is fair (45/100, worse than 65% of steel grades); weldability poor (15/100); 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. 905M39 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with 905M39
Is 905M39 easy to machine?
Machine fully in the hardened-and-tempered condition with carbide tooling (approx. 50 % of 1212); rough, stress-relieve at 550–600 °C, then finish and leave 0.02–0.05 mm for post-nitride lapping/grinding only.
Can 905M39 be welded?
Not recommended — high carbon plus 1.1 % Al gives severe cracking and destroys the nitriding response; if unavoidable, preheat 300–350 °C, low-hydrogen consumables and immediate post-weld temper.
Can 905M39 be formed, bent or molded?
Hot forge 1150–850 °C then slow-cool/anneal; cold forming is impractical — harden 900–930 °C oil quench and temper 600–680 °C to the required BS 970 condition before nitriding at 500–530 °C.
905M39 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 | 0.4 – 0.8 | 0.6 |
| P | ≤ 0.04 | |
| Smax; low-S variants for cleanliness | ≤ 0.04 | |
| Cr | 1.4 – 1.8 | 1.6 |
| Mo | 0.1 – 0.25 | 0.2 |
| Alnitride-former, gives the very hard AlN case | 0.9 – 1.3 | 1.1 |
| Niresidual, not specified in all editions | ≤ 0.4 | |
| Fe | balance |
What surface finishes work on 905M39?
Nitriding itself is the primary finish (compound layer can be oxidised black); otherwise phosphate, black oxide, or paint — chrome/nickel plating requires the case to be stripped or masked, and no anodising applies.
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 905M39 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- Similar grades
- 9255
How much does 905M39 cost?
905M39 is a standard-cost steel ($$), cheaper than about 71% 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.
905M39 — frequently asked
What is 905M39 used for?
905M39 is typically used for leaf springs, coil springs and stabilizer bars. In short: high-fatigue spring steel; strong nitriding response; effectively non-weldable.
What is the yield strength of 905M39?
905M39 has a typical yield strength of 710 MPa (103 ksi) and a tensile strength of 925 MPa (134 ksi) — stronger than 82% of steel grades. Strength varies by condition: see the 5 listed tempers.
Is 905M39 easy to machine?
Reasonably — machinability is rated fair (45/100, worse than 65% of steel grades). Machine fully in the hardened-and-tempered condition with carbide tooling (approx. 50 % of 1212); rough, stress-relieve at 550–600 °C, then finish and leave 0.02–0.05 mm for post-nitride lapping/grinding only.
Can 905M39 be welded?
Not readily — weldability is rated poor (15/100). Not recommended — high carbon plus 1.1 % Al gives severe cracking and destroys the nitriding response; if unavoidable, preheat 300–350 °C, low-hydrogen consumables and immediate post-weld temper.
What surface finishes work on 905M39?
Nitriding itself is the primary finish (compound layer can be oxidised black); otherwise phosphate, black oxide, or paint — chrome/nickel plating requires the case to be stripped or masked, and no anodising applies.
Can 905M39 be formed, bent or molded?
Hot forge 1150–850 °C then slow-cool/anneal; cold forming is impractical — harden 900–930 °C oil quench and temper 600–680 °C to the required BS 970 condition before nitriding at 500–530 °C.
What is the maximum service temperature of 905M39?
905M39 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 905M39-T and 905M39-ANN?
T is the default condition — standard stock condition: tough core for general nitrided shafts, spindles, gears and valve components. ANN: choose for heavy machining or cold work before the customer's own harden-temper-nitride cycle. Yield strength is 710 MPa in T versus 450 MPa in ANN.
How much does 905M39 cost?
905M39 is a standard-cost steel ($$), cheaper than about 71% 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 970-1: Wrought steels for mechanical and allied engineering purposes (905M39, ex-En41B) — BSI (1991)
- GB/T 3077 Alloy structural steels (38CrMoAlA equivalent) — SAC (2015)
- ASM Handbook Vol.4A — Steel Heat Treating Fundamentals and Processes (nitriding steels) — ASM International (2013)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels and High-Performance Alloys — ASM International (1990)
- 905M39 / EN41B nitriding steel bar datasheet — UK alloy-steel stockholders (e.g. West Yorkshire Steel, Smiths) (2023)
- 38CrMoAlA — Mysteel / 1688 (2026)
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.