Steel 37Mo2 +AC (Spheroidize annealed)
Heat-treated state
EN 37Mo2
Pick when the part is cold formed, cold extruded or heavily turned/threaded before hardening — softest and most ductile condition.
Values for the +AC condition
Other 37Mo2 tempers and conditions
37Mo2 is listed in 10 conditions; see the grade overview at 37Mo2.
Compare all 10 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
+ACThis page Spheroidize annealed | Pick when the part is cold formed, cold extruded or heavily turned/threaded before hardening — softest and most ductile condition. | 300 | 520 | 26 | 155 HB | — |
Annealed | Choose for lowest hardness before heavy machining or as delivery condition for later hardening. | 320 | 560 | 22 | 165 HB | — |
Treated to ferrite–pearlite structure / hardness range | Use when a uniform, predictable machining structure and hardness band is specified for automated turning lines. | 350 | 600 | 20 | 10 HRC | 8.3 % IACS |
Normalized | Refines grain and homogenizes forged or hot-rolled stock; good baseline for medium-duty shafts not requiring full Q&T. | 375 | 630 | 20 | 185 HB | — |
Hot rolled | Cheapest stock form for parts that will be fully heat treated after rough machining. | 380 | 650 | 18 | 12 HRC | 8 % IACS |
+QTDefault Quenched and tempered | Standard stocked condition for finished shafts, gear blanks and pins — balanced strength and toughness. | 550 | 800 | 15 | 22 HRC | — |
+QT + induction hardened surface | Select for shaft journals, splines and gear teeth needing a hard wear surface on a tough Q&T core. | 550 | 800 | 13 | 54 HRC | — |
Cold drawn | Use for close-tolerance bright bar where the part is finished without further heat treatment. | 590 | 700 | 10 | 17 HRC | 7.9 % IACS |
+QT | Low-temperature temper for small-diameter, highly loaded shafts and pins where toughness demands are moderate. | 720 | 970 | 12 | 31 HRC | — |
Hardened | Order +H when a Jominy hardenability band is contractually required, or for the as-quenched martensitic state prior to tempering. | 1,300 | 1,700 | 3 | 52 HRC | — |
What is 37Mo2 +AC?
37Mo2 +AC is 37Mo2 heat treated to +AC — pick when the part is cold formed, cold extruded or heavily turned/threaded before hardening — softest and most ductile condition. 37Mo2 +AC has a yield strength of 300 MPa (43.5 ksi) and a tensile strength of 520 MPa (75.4 ksi) — weaker than 86% of steel grades. Elongation at break is 26% and the elastic modulus is 210 GPa (30.5 Msi). 37Mo2 +AC has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,420°C (2,588 °F). +QT is the default condition FabDigit quotes; +AC is available on request or by drawing note.
Advantages
- Easy to machine — 64/100, better than 92% of steel grades
- Low embodied carbon — 1.9 kg CO₂/kg, better than 92% of steel grades
- Ductile — tolerates forming and impact — 26%, better than 82% of steel grades
- Forms and bends easily — 62/100, better than 78% of steel grades
Limitations
- Low strength — 300 MPa (43.5 ksi), worse than 86% of steel grades
- Low fracture toughness — 65 MPa·√m (59.2 ksi·√in), worse than 75% of steel grades
37Mo2 +AC properties
Typical room-temperature values for 37Mo2 +AC; 12 are specific to this condition. Other listed values are 37Mo2 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
37Mo2 +AC has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,420°C (2,588 °F).
Mechanical16
37Mo2 +AC has a yield strength of 300 MPa (43.5 ksi) and a tensile strength of 520 MPa (75.4 ksi) — weaker than 86% of steel grades. Elongation at break is 26% and the elastic modulus is 210 GPa (30.5 Msi).
Thermal6
37Mo2 +AC is rated for continuous service to 400°C (752 °F). It conducts heat at 42 W/m·K (24.3 BTU/hr·ft·°F), worse than 56% of steel grades. Thermal expansion is 12.3 µm/m·K (6.83 µin/in·°F).
Electrical3
37Mo2 +AC conducts electricity at 7.8 % IACS, worse than 57% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (11/100), worse than 73% of steel grades.
Sustainability4
Producing a kilogram of 37Mo2 +AC takes about 27 MJ of energy and emits 1.9 kg of CO₂ — less than 59% of steel grades. Typical recycled content is 30%.
Manufacturability7
37Mo2 +AC's machinability is good (64/100, better than 92% of steel grades); weldability fair (50/100); formability good (62/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 37Mo2 +AC
Is 37Mo2 easy to machine?
Machine in +A/+AC or +FP (150–185 HB) with carbide tooling; at 235 HB (+QT) reduce speed ~25 % and use rigid setups; grind after hardening.
Can 37Mo2 be welded?
Weldable with low-hydrogen consumables but Mo + 0.37 C means preheat 200–300 °C, control interpass and stress-relieve/temper 550–650 °C after welding.
Can 37Mo2 be formed, bent or molded?
Cold form only in the spheroidize-annealed (+AC) condition; otherwise hot forge 1100–850 °C followed by normalizing or Q&T.
What surface finishes work on 37Mo2?
No natural corrosion resistance — apply phosphate + oil, zinc or hard chrome plating, black oxide or paint; nitriding gives a wear surface without distortion.
37Mo2 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 |
|---|---|---|
| Cdesignation 37 = ~0.37 % C | 0.32 – 0.42 | 0.37 |
| Si | ≤ 0.4 | 0.25 |
| Mn | 0.5 – 0.8 | 0.65 |
| P | ≤ 0.04 | — |
| Smax; lower for +QT quality grades | ≤ 0.04 | — |
| MoMo2 = ~0.25 % Mo | 0.2 – 0.3 | 0.25 |
| Crresidual | ≤ 0.3 | — |
| Niresidual | ≤ 0.3 | — |
| Fe | balance | — |
37Mo2 +AC — frequently asked
What is 37Mo2 +AC used for?
37Mo2 +AC is typically used for shafts, axles and gears. In short: moderate-strength Mo shaft steel; limited weldability, preheat required; suits induction hardening.
What is the yield strength of 37Mo2 +AC?
37Mo2 +AC has a typical yield strength of 300 MPa (43.5 ksi) and a tensile strength of 520 MPa (75.4 ksi) — weaker than 86% of steel grades. Strength varies by condition: see the 10 listed tempers.
Is 37Mo2 +AC easy to machine?
Reasonably — machinability is rated good (64/100, better than 92% of steel grades). Machine in +A/+AC or +FP (150–185 HB) with carbide tooling; at 235 HB (+QT) reduce speed ~25 % and use rigid setups; grind after hardening.
Can 37Mo2 +AC be welded?
With care — weldability is rated fair (50/100). Weldable with low-hydrogen consumables but Mo + 0.37 C means preheat 200–300 °C, control interpass and stress-relieve/temper 550–650 °C after welding.
What surface finishes work on 37Mo2 +AC?
No natural corrosion resistance — apply phosphate + oil, zinc or hard chrome plating, black oxide or paint; nitriding gives a wear surface without distortion.
Can 37Mo2 +AC be formed, bent or molded?
Cold form only in the spheroidize-annealed (+AC) condition; otherwise hot forge 1100–850 °C followed by normalizing or Q&T.
What is the maximum service temperature of 37Mo2 +AC?
37Mo2 +AC 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.
Sources
- EN 10083-3 Steels for quenching and tempering — alloy steels — CEN (2006)
- EN 10084 Case hardening steels — technical delivery conditions (delivery states +A, +AC, +FP, +TH) — CEN (2008)
- EN 10027-2 Designation systems for steels — steel numbers (1.5418) — CEN (2015)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol.4 — Heat Treating — ASM International (1991)
- Stahlschlüssel (Key to Steel) — Mo alloy structural steels — Verlag Stahlschlüssel Wegst (2019)
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.