Steel 905M39-ANN (Annealed)
Heat-treated state
BS 905M39
Choose for heavy machining or cold work before the customer's own harden-temper-nitride cycle.
Values for the ANN condition
Other 905M39 tempers and conditions
905M39 is listed in 5 conditions; see the grade overview at 905M39.
Compare all 5 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
ANNThis page 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 | — |
What is 905M39-ANN?
905M39-ANN is 905M39 heat treated to ANN — choose for heavy machining or cold work before the customer's own harden-temper-nitride cycle. 905M39-ANN has a yield strength of 450 MPa (65.3 ksi) and a tensile strength of 700 MPa (102 ksi) — stronger than 52% of steel grades. Elongation at break is 20% and the elastic modulus is 210 GPa (30.5 Msi). 905M39-ANN 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). T is the default condition FabDigit quotes; ANN is available on request or by drawing note.
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
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
905M39-ANN properties
Typical room-temperature values for 905M39-ANN; 11 are specific to this condition. Other listed values are 905M39 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
905M39-ANN 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-ANN has a yield strength of 450 MPa (65.3 ksi) and a tensile strength of 700 MPa (102 ksi) — stronger than 52% of steel grades. Elongation at break is 20% and the elastic modulus is 210 GPa (30.5 Msi).
Thermal6
905M39-ANN 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-ANN 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-ANN 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-ANN's machinability is good (55/100, better than 62% of steel grades); weldability poor (15/100); formability fair (35/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 905M39-ANN
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.
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.
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 | — |
905M39-ANN — frequently asked
What is 905M39-ANN used for?
905M39-ANN 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-ANN?
905M39-ANN has a typical yield strength of 450 MPa (65.3 ksi) and a tensile strength of 700 MPa (102 ksi) — stronger than 52% of steel grades. Strength varies by condition: see the 5 listed tempers.
Is 905M39-ANN easy to machine?
Reasonably — machinability is rated good (55/100, better than 62% 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-ANN 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-ANN?
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-ANN 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-ANN?
905M39-ANN 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.
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. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.