Steel 40CrMnMo
GB 40CrMnMo
40CrMnMo is a quenched-and-tempered Cr-Mn-Mo alloy structural steel in the 42CrMo4 group, with manganese and molybdenum added for deep hardenability in large sections.
Reference datasheet — 40CrMnMo 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 QT600 condition
40CrMnMo tempers and conditions
40CrMnMo is supplied in 11 conditions, soft to hard. QT600 is the default FabDigit quotes; the values on this page are for it.
Compare all 11 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Solution annealed | Softest condition for deep machining, cold shearing or before final quench-and-temper. | 390 | 660 | 22 | 197 HB | — |
Hot rolled | Cheapest mill condition for stock that will be re-heat-treated after rough machining. | 520 | 820 | 15 | 21 HRC | 8 % IACS |
Normalized | Grain-refining pre-treatment for large forgings; also a low-cost medium-strength delivery state. | 600 | 900 | 16 | 26 HRC | 8 % IACS |
Cold drawn | Bright, size-accurate small-diameter bar for shafts and pins machined without further heat treatment. | 720 | 860 | 10 | 25 HRC | 8 % IACS |
Q&T 28–32 HRC (≈269–302 HB) pre-hardened block | Pre-hardened plate/block for large plastic moulds and jig plates machined in the delivered state. | 820 | 980 | 15 | 30 HRC | 8 % IACS |
QT600Default oil quench 850 °C + temper 600 °C ( , ≥980 MPa) | Standard GB/T 3077 delivery condition — best strength/toughness balance for shafts, gears and heavy forgings. | 850 | 1,030 | 14 | 31 HRC | — |
Nitrided | Choose when a hard, fatigue-boosting 0.2–0.5 mm case is needed on a tough Q&T core with minimal distortion. | 850 | 1,030 | 13 | 56 HRC | 8 % IACS |
Induction hardened | For journal and spline wear surfaces on Q&T shafts needing a hard, compressively stressed skin. | 850 | 1,030 | 14 | 54 HRC | 7.5 % IACS |
Q&T 32–36 HRC (≈302–341 HB) | Higher-hardness Q&T for mill rolls, mandrels and wear-loaded shafts still machinable with carbide. | 970 | 1,120 | 12 | 34 HRC | 8 % IACS |
oil quench + temper 550 °C (≈38–42 HRC) | Higher-strength temper for highly loaded medium-section parts where toughness can be traded for strength. | 1,150 | 1,300 | 11 | 40 HRC | — |
oil quench + temper 450 °C (≈45–48 HRC) | Maximum practical hardness temper for wear parts; low toughness and temper-brittleness risk, use only in small sections. | 1,350 | 1,500 | 9 | 46 HRC | 7.5 % IACS |
What is 40CrMnMo?
40CrMnMo is a quenched-and-tempered Cr-Mn-Mo alloy structural steel in the 42CrMo4 group, with manganese and molybdenum added for deep hardenability in large sections. It is used for heavy shafts, rolls and other large forgings, and is supplied hot-rolled, annealed, normalized, cold-drawn and in several Q&T hardness bands (28-32 HRC and 32-36 HRC), as well as nitrided and induction-hardened. Default Q&T properties are 850 MPa yield, 1030 MPa tensile, 14 % elongation and 302 HB (31 HRC), with service to 400 °C. It has no bare corrosion resistance and CE ≈ 0.85 makes welding demanding; 42CrMo4 covers smaller sections. 40CrMnMo 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). 40CrMnMo has a yield strength of 850 MPa (123 ksi) and a tensile strength of 1,030 MPa (149 ksi) — stronger than 88% of steel grades. Elongation at break is 14% and the elastic modulus is 210 GPa (30.5 Msi).
What is 40CrMnMo used for?
- large shafts
- rolling mill parts
- heavy forgings
Advantages
- High strength — 850 MPa (123 ksi), better than 88% of steel grades
Limitations
- Limited ductility — 14%, worse than 75% of steel grades
40CrMnMo properties
Typical room-temperature values for 40CrMnMo-QT600; bars are the position among steel grades.
Physical3
40CrMnMo 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
40CrMnMo has a yield strength of 850 MPa (123 ksi) and a tensile strength of 1,030 MPa (149 ksi) — stronger than 88% of steel grades. Elongation at break is 14% and the elastic modulus is 210 GPa (30.5 Msi).
Thermal6
40CrMnMo 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
40CrMnMo conducts electricity at 8 % IACS, better than 55% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of 40CrMnMo takes about 30 MJ of energy and emits 2.1 kg of CO₂ — more than 56% of steel grades. Typical recycled content is 30%.
Manufacturability6
40CrMnMo's machinability is fair (52/100, better than 52% of steel grades); weldability fair (35/100); formability poor (25/100).
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. 40CrMnMo is highlighted; hover a dot for its name, or open the interactive family chart.
Working with 40CrMnMo
Is 40CrMnMo easy to machine?
Rough machine annealed (≈197 HB) then Q&T; at 300 HB use rigid setups, coated carbide at 90–140 m/min and positive rake to control work-hardening and built-up edge.
Can 40CrMnMo be welded?
CE ≈ 0.85 — preheat 250–350 °C, low-hydrogen consumables, interpass control and immediate post-weld temper at 30–50 °C below the part's tempering temperature; avoid welding above 40 HRC.
Can 40CrMnMo be formed, bent or molded?
Hot forge 1150–850 °C with slow cooling or immediate anneal to prevent flake/quench cracks; cold forming limited to the annealed state and gentle bends.
40CrMnMo 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 |
|---|---|---|
| CGB/T 3077 | 0.37 – 0.45 | 0.41 |
| Si | 0.17 – 0.37 | 0.27 |
| Mnraised vs 42CrMo4 for hardenability | 0.9 – 1.2 | 1.05 |
| Cr | 0.9 – 1.2 | 1.05 |
| Mo | 0.2 – 0.3 | 0.25 |
| Niresidual | ≤ 0.3 | |
| Curesidual | ≤ 0.25 | |
| P0.025 max for high-grade quality | ≤ 0.03 | |
| S0.025 max for high-grade quality | ≤ 0.03 | |
| Fe | balance |
What surface finishes work on 40CrMnMo?
No corrosion resistance bare — protect with oil, phosphating, black oxide, paint, hard chrome or nitriding; VD-degassed heats polish to mould-grade SPI-B finishes.
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 40CrMnMo in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- Similar grades
- 42CrMo4
How much does 40CrMnMo cost?
40CrMnMo 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.
40CrMnMo — frequently asked
What is 40CrMnMo used for?
40CrMnMo is typically used for large shafts, rolling mill parts and heavy forgings. In short: deep-hardening 42CrMo4 type; suits large forged sections; nitridable and induction-hardenable.
What is the yield strength of 40CrMnMo?
40CrMnMo has a typical yield strength of 850 MPa (123 ksi) and a tensile strength of 1,030 MPa (149 ksi) — stronger than 88% of steel grades. Strength varies by condition: see the 11 listed tempers.
Is 40CrMnMo easy to machine?
Reasonably — machinability is rated fair (52/100, better than 52% of steel grades). Rough machine annealed (≈197 HB) then Q&T; at 300 HB use rigid setups, coated carbide at 90–140 m/min and positive rake to control work-hardening and built-up edge.
Can 40CrMnMo be welded?
With care — weldability is rated fair (35/100). CE ≈ 0.85 — preheat 250–350 °C, low-hydrogen consumables, interpass control and immediate post-weld temper at 30–50 °C below the part's tempering temperature; avoid welding above 40 HRC.
What surface finishes work on 40CrMnMo?
No corrosion resistance bare — protect with oil, phosphating, black oxide, paint, hard chrome or nitriding; VD-degassed heats polish to mould-grade SPI-B finishes.
Can 40CrMnMo be formed, bent or molded?
Hot forge 1150–850 °C with slow cooling or immediate anneal to prevent flake/quench cracks; cold forming limited to the annealed state and gentle bends.
What is the maximum service temperature of 40CrMnMo?
40CrMnMo 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.
What is the difference between 40CrMnMo-QT600 and 40CrMnMo-QT450?
QT600 is the default condition — standard GB/T 3077 delivery condition — best strength/toughness balance for shafts, gears and heavy forgings. QT450: maximum practical hardness temper for wear parts; low toughness and temper-brittleness risk, use only in small sections. Yield strength is 850 MPa in QT600 versus 1,350 MPa in QT450.
How much does 40CrMnMo cost?
40CrMnMo 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
- GB/T 3077 Alloy structural steels (2015)
- EN 10083-3 Steels for quenching and tempering — alloy steels (42CrMo4 comparison) — CEN (2006)
- 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)
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.