Steel 42CrMo
GB 42CrMo
42CrMo is the Chinese GB/T 3077 chromium-molybdenum medium-carbon low-alloy structural steel, essentially equivalent to AISI 4140/4142 and EN 42CrMo4 (1.7225).
Values for the HR condition
42CrMo tempers and conditions
42CrMo is supplied in 9 conditions, soft to hard. HR is the default FabDigit quotes; the values on this page are for it.
Compare all 9 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
full/spheroidize anneal, ≤217 HB | Softest condition — choose for heavy machining, deep drilling or cold upsetting before final hardening. | 450 | 700 | 22 | 200 HB | — |
HRDefault Hot rolled | Cheapest stock form for parts that will be heat treated (or lightly loaded) after machining. | 570 | 880 | 15 | 22 HRC | — |
austenitize ~860 °C, air cool | Uniform fine-grain structure for forgings and large sections before final Q&T or for moderate-strength service. | 650 | 1,000 | 18 | 29 HRC | — |
Cold rolled | Thin strip/plate form (often annealed after rolling) for stamped or laser-cut blanks that will be hardened later. | 660 | 820 | 12 | 23 HRC | 7.8 % IACS |
Cold drawn | Close tolerance, bright surface bar for shafting and turned parts that need little further machining. | 780 | 930 | 11 | 26 HRC | — |
Tempered high for toughness / sour service | Pick when NACE MR0175 (≤22 HRC alternative not required) or maximum impact toughness and machinability after heat treatment matter. | 860 | 1,000 | 17 | 30 HRC | — |
Quenched and tempered | Standard high-strength delivery condition for shafts, gears and bolting where 1080 MPa min tensile is specified. | 960 | 1,120 | 14 | 36 HRC | — |
Q&T + gas/plasma nitrided | Choose for wear surfaces (gears, spindles, hydraulic rods) where the Q&T core strength is kept and a hard, distortion-free case is added; hardness values below are surface, core equals Q&T. | 960 | 1,120 | 13 | 36 HRC | — |
Tempered for higher strength | Highest practical hardness that keeps useful toughness — gears, couplings, high-strength studs and drill collars. | 1,050 | 1,180 | 12 | 36 HRC | — |
What is 42CrMo?
42CrMo is the Chinese GB/T 3077 chromium-molybdenum medium-carbon low-alloy structural steel, essentially equivalent to AISI 4140/4142 and EN 42CrMo4 (1.7225). It is the workhorse grade for quenched-and-tempered shafts, gears, bolting, drill collars and hydraulic components because it through-hardens well in medium sections and gives 1000–1200 MPa tensile with good toughness. Its limits are poor cold formability, restricted weldability (preheat and post-weld temper required to avoid HAZ cracking) and essentially no corrosion resistance, so plating, oiling or paint is mandatory. 42CrMo has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,416°C (2,581 °F). 42CrMo has a yield strength of 570 MPa (82.7 ksi) and a tensile strength of 880 MPa (128 ksi) — stronger than 74% of steel grades. Elongation at break is 15% and the elastic modulus is 210 GPa (30.5 Msi).
What is 42CrMo used for?
- Drive shafts
- Crankshafts
- Gears and pinions
- High-strength bolting and studs
- Hydraulic cylinder rods
- Drill collars
- Forged couplings and flanges
- Axle and spindle shafts
42CrMo properties
Typical room-temperature values for 42CrMo-HR; bars are the position among steel grades.
Physical3
42CrMo has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,416°C (2,581 °F).
Mechanical15
42CrMo has a yield strength of 570 MPa (82.7 ksi) and a tensile strength of 880 MPa (128 ksi) — stronger than 74% of steel grades. Elongation at break is 15% and the elastic modulus is 210 GPa (30.5 Msi).
Thermal6
42CrMo is rated for continuous service to 425°C (797 °F). It conducts heat at 42.6 W/m·K (24.6 BTU/hr·ft·°F), worse than 51% of steel grades. Thermal expansion is 12.3 µm/m·K (6.83 µin/in·°F).
Electrical3
42CrMo conducts electricity at 7.8 % IACS, worse than 57% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of 42CrMo takes about 29 MJ of energy and emits 2.3 kg of CO₂ — less than 53% of steel grades. Typical recycled content is 30%.
Manufacturability7
42CrMo's machinability is fair (50/100, worse than 53% of steel grades); weldability poor (30/100); 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. 42CrMo is highlighted; hover a dot for its name, or open the interactive family chart.
Working with 42CrMo
Is 42CrMo easy to machine?
Machine in the annealed or ≤32 HRC Q&T condition with rigid setups, carbide inserts and generous coolant; above 38 HRC switch to grinding or CBN.
Can 42CrMo be welded?
Weldable with low-hydrogen consumables but requires 200–350 °C preheat, controlled interpass temperature and immediate post-weld temper (~600 °C) to avoid HAZ cracking.
Can 42CrMo be formed, bent or molded?
Hot forge/upset at 1150–850 °C then normalize; cold bending is limited — anneal first and use generous radii.
Manufacturability
The process limits FabDigit's quote engine applies to 42CrMo. Design inside these and the part quotes instantly; outside them it routes to an engineer.
CNC machining
| Machinability | Better50 / 100 |
|---|---|
| ISO material group | P.2 |
| Cutting speed (rough / finish) | 180 / 210 m/min |
| Minimum wall | 0.8 mm |
| Minimum internal radius | 1 mm |
| Drill depth limit | 5× diameter |
| Best surface (machined / polished) | Ra 1.6 / — |
| Hardenable after machining | No |
Sheet metal
| Formability | Fair25 / 100 |
|---|---|
| Weldability | Better30 / 100 |
42CrMo 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 | 0.38 – 0.45 | 0.42 |
| Si | 0.17 – 0.37 | 0.27 |
| Mn | 0.5 – 0.8 | 0.65 |
| Cr | 0.9 – 1.2 | 1.05 |
| Mo | 0.15 – 0.25 | 0.2 |
| Niresidual limit | ≤ 0.3 | |
| Curesidual limit | ≤ 0.3 | |
| P | ≤ 0.03 | |
| S | ≤ 0.03 | |
| Fe | balance |
What surface finishes work on 42CrMo?
No anodizing; use black oxide, manganese phosphate, zinc or hard-chrome plating (bake to avoid hydrogen embrittlement above ~35 HRC), nitriding or paint for corrosion protection.
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).
Plating
CVD Coating
Black / Phosphate
Thermal Spray
Equivalent designations
Standards and trade names that resolve to Steel 42CrMo in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
How much does 42CrMo cost?
42CrMo is a standard-cost steel ($$), cheaper than about 61% 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.
42CrMo — frequently asked
What is 42CrMo used for?
42CrMo is typically used for drive shafts, crankshafts, gears and pinions, high-strength bolting and studs, hydraulic cylinder rods and drill collars. In short: workhorse Cr-Mo machining bar.
What is the yield strength of 42CrMo?
42CrMo has a typical yield strength of 570 MPa (82.7 ksi) and a tensile strength of 880 MPa (128 ksi) — stronger than 74% of steel grades. Strength varies by condition: see the 9 listed tempers.
Is 42CrMo easy to machine?
Reasonably — machinability is rated fair (50/100, worse than 53% of steel grades). Machine in the annealed or ≤32 HRC Q&T condition with rigid setups, carbide inserts and generous coolant; above 38 HRC switch to grinding or CBN.
Can 42CrMo be welded?
Not readily — weldability is rated poor (30/100). Weldable with low-hydrogen consumables but requires 200–350 °C preheat, controlled interpass temperature and immediate post-weld temper (~600 °C) to avoid HAZ cracking.
What surface finishes work on 42CrMo?
No anodizing; use black oxide, manganese phosphate, zinc or hard-chrome plating (bake to avoid hydrogen embrittlement above ~35 HRC), nitriding or paint for corrosion protection.
Can 42CrMo be formed, bent or molded?
Hot forge/upset at 1150–850 °C then normalize; cold bending is limited — anneal first and use generous radii.
What is the maximum service temperature of 42CrMo?
42CrMo is rated for continuous use to about 425°C (797 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 42CrMo-HR and 42CrMo-CD?
HR is the default condition — cheapest stock form for parts that will be heat treated (or lightly loaded) after machining. CD: close tolerance, bright surface bar for shafting and turned parts that need little further machining. Yield strength is 570 MPa in HR versus 780 MPa in CD.
How much does 42CrMo cost?
42CrMo is a standard-cost steel ($$), cheaper than about 61% 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.
Can FabDigit make parts in 42CrMo?
Yes — 42CrMo is available for CNC machining and sheet metal with instant online pricing. Upload a STEP file to get a price and a DFM check.
Sources
- GB/T 3077 Alloy structural steels — SAC (2015)
- EN 10083-3 (42CrMo4, 1.7225) — CEN (2006)
- ASTM A29/A29M & SAE J404 (4140) — ASTM / SAE (2020)
- ASM Handbook Vol.1 Properties and Selection: Irons, Steels — ASM International (1990)
- ASM Handbook Vol.19 Fatigue and Fracture — ASM International (1996)
- Machinery's Handbook, machinability ratings — Industrial Press (2020)
- NACE MR0175/ISO 15156 hardness limits for sour service — NACE/ISO (2015)
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.