Steel 42CrMo · hardness band
Steel 42CrMo Q&T 34-38 HRC
Properties of the Q&T 34-38 HRC condition, compared with the other 42CrMo tempers.
Highest practical hardness that keeps useful toughness — gears, couplings, high-strength studs and drill collars.
What is 42CrMo Q&T 34-38 HRC?
42CrMo Q&T 34-38 HRC is 42CrMo heat treated to Q&T 34-38 HRC — highest practical hardness that keeps useful toughness — gears, couplings, high-strength studs and drill collars. 42CrMo Q&T 34-38 HRC has a yield strength of 1,050 MPa (152 ksi) and a tensile strength of 1,180 MPa (171 ksi) — stronger than 93% of steel grades. Elongation at break is 12% and the elastic modulus is 210 GPa (30.5 Msi). 42CrMo Q&T 34-38 HRC 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). HR is the default condition FabDigit quotes; Q&T 34-38 HRC is available on request or by drawing note.
Advantages
- High strength — 1,050 MPa (152 ksi), better than 93% of steel grades
Limitations
- Difficult to machine — 33/100, worse than 86% of steel grades
- Limited ductility — 12%, worse than 84% of steel grades
42CrMo Q&T 34-38 HRC properties
Typical room-temperature values for 42CrMo Q&T 34-38 HRC — 11 properties are specific to this condition; the rest are grade-level values shared by every 42CrMo temper. Each bar shows where the value sits among the steel grades in FabDigit's library — further right is higher.
Physical3
42CrMo Q&T 34-38 HRC 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 Q&T 34-38 HRC has a yield strength of 1,050 MPa (152 ksi) and a tensile strength of 1,180 MPa (171 ksi) — stronger than 93% of steel grades. Elongation at break is 12% and the elastic modulus is 210 GPa (30.5 Msi).
Thermal6
42CrMo Q&T 34-38 HRC 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), better than 50% of steel grades. Thermal expansion is 12.3 µm/m·K (6.83 µin/in·°F).
Electrical3
42CrMo Q&T 34-38 HRC conducts electricity at 7.8 % IACS, worse than 58% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of 42CrMo Q&T 34-38 HRC 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 Q&T 34-38 HRC's machinability is poor (33/100, worse than 86% of steel grades); weldability poor (30/100); formability poor (25/100).
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Other 42CrMo tempers and conditions
42CrMo is also supplied in 8 other conditions. The full side-by-side table is on the 42CrMo overview.
- HRDefaultCheapest stock form for parts that will be heat treated (or lightly loaded) after machining.570 MPa yield · 22 HRC
- Q&T 34-38 HRCHighest practical hardness that keeps useful toughness — gears, couplings, high-strength studs and drill collars.1,050 MPa yield · 36 HRC
- Q&TStandard high-strength delivery condition for shafts, gears and bolting where 1080 MPa min tensile is specified.960 MPa yield · 36 HRC
- Q&T+NitridedChoose 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 MPa yield · 36 HRC
- Q&T 28-32 HRCPick when NACE MR0175 (≤22 HRC alternative not required) or maximum impact toughness and machinability after heat treatment matter.860 MPa yield · 30 HRC
- CDClose tolerance, bright surface bar for shafting and turned parts that need little further machining.780 MPa yield · 26 HRC
- NormalizedUniform fine-grain structure for forgings and large sections before final Q&T or for moderate-strength service.650 MPa yield · 29 HRC
- AnnealedSoftest condition — choose for heavy machining, deep drilling or cold upsetting before final hardening.450 MPa yield · 200 HB
Working with 42CrMo Q&T 34-38 HRC
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.
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.
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 | — |
42CrMo Q&T 34-38 HRC — frequently asked
What is 42CrMo Q&T 34-38 HRC used for?
42CrMo Q&T 34-38 HRC 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 Q&T 34-38 HRC?
42CrMo Q&T 34-38 HRC has a typical yield strength of 1,050 MPa (152 ksi) and a tensile strength of 1,180 MPa (171 ksi) — stronger than 93% of steel grades. Strength varies by condition: see the 9 listed tempers.
Is 42CrMo Q&T 34-38 HRC easy to machine?
Not especially — machinability is rated poor (33/100, worse than 86% 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 Q&T 34-38 HRC 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 Q&T 34-38 HRC?
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 Q&T 34-38 HRC 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 Q&T 34-38 HRC?
42CrMo Q&T 34-38 HRC 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.
Can FabDigit make parts in 42CrMo Q&T 34-38 HRC?
Yes — 42CrMo Q&T 34-38 HRC 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. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.