Steel 40CrNiMoA Q&T 38-42 HRC
Hardness band
GB 40CrNiMoA · AISI/SAE 4340
Q&T 38-42 HRC = lower temper
Use for higher-strength ~1300 MPa parts such as aerospace fittings and heavy-duty bolts where some ductility is still needed.
Values for the Q&T 38-42 HRC condition
Other 40CrNiMoA tempers and conditions
40CrNiMoA is listed in 10 conditions; see the grade overview at 40CrNiMoA.
Compare all 10 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
full anneal ~820–840 °C, slow cool | Softest condition for deep machining, cold forming or as a pre-heat-treat stock; hardness capped at 269 HB per GB/T 3077. | 470 | 745 | 22 | 217 HB | — |
Hot rolled | Cheapest mill condition, bought as forging or machining blank when the shop will heat treat afterwards; properties vary with section and cooling rate. | 620 | 950 | 14 | 30 HRC | 7 % IACS |
Cold drawn | Bright, close-tolerance bar for direct machining of moderately loaded parts without further heat treatment. | 720 | 860 | 12 | 24 HRC | 7 % IACS |
~860–880 °C, air cool | Uniform, refined structure for forgings before final Q&T; already strong but with limited ductility because of the air-hardened bainite/martensite. | 860 | 1,280 | 12 | 39 HRC | — |
High-temper condition | Pick when toughness and machinability matter more than strength, e.g. large forged shafts and pressure-containing parts. | 860 | 1,000 | 18 | 30 HRC | — |
Q&TDefault Quenched and tempered | Standard stocked condition: balanced ~1000–1100 MPa strength with high toughness for shafts, gears and high-strength fasteners. | 950 | 1,080 | 16 | 34 HRC | — |
Mid-temper condition | Most common ordered hardness band for gears, connecting rods and driveline shafts; good strength/toughness compromise. | 1,000 | 1,100 | 15 | 34 HRC | — |
Q&T 38-42 HRCThis page Lower temper | Use for higher-strength ~1300 MPa parts such as aerospace fittings and heavy-duty bolts where some ductility is still needed. | 1,200 | 1,300 | 12 | 40 HRC | — |
Low temper | High-strength ~1500 MPa condition for torsion bars, landing-gear-type parts and tooling; toughness and machinability drop sharply. | 1,350 | 1,500 | 10 | 44 HRC | — |
Quench and stress-relief temper | Maximum strength (~1800 MPa) condition for wear parts and tooling; brittle, notch- and hydrogen-sensitive, so avoid stress concentrations and plate only with post-bake. | 1,600 | 1,800 | 8 | 50 HRC | — |
What is 40CrNiMoA Q&T 38-42 HRC?
40CrNiMoA Q&T 38-42 HRC is 40CrNiMoA heat treated to Q&T 38-42 HRC — use for higher-strength ~1300 MPa parts such as aerospace fittings and heavy-duty bolts where some ductility is still needed. 40CrNiMoA Q&T 38-42 HRC has a yield strength of 1,200 MPa (174 ksi) and a tensile strength of 1,300 MPa (189 ksi) — stronger than 94% of steel grades. Elongation at break is 12% and the elastic modulus is 207 GPa (30 Msi). 40CrNiMoA Q&T 38-42 HRC 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). Q&T is the default condition FabDigit quotes; Q&T 38-42 HRC is available on request or by drawing note.
Advantages
- High strength — 1,200 MPa (174 ksi), better than 94% of steel grades
- Polishes to a fine finish — 65/100, better than 78% of steel grades
Limitations
- Difficult to machine — 30/100, worse than 89% of steel grades
- Limited ductility — 12%, worse than 84% of steel grades
40CrNiMoA Q&T 38-42 HRC properties
Typical room-temperature values for 40CrNiMoA Q&T 38-42 HRC; 13 are specific to this condition. Other listed values are 40CrNiMoA reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
40CrNiMoA Q&T 38-42 HRC 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
40CrNiMoA Q&T 38-42 HRC has a yield strength of 1,200 MPa (174 ksi) and a tensile strength of 1,300 MPa (189 ksi) — stronger than 94% of steel grades. Elongation at break is 12% and the elastic modulus is 207 GPa (30 Msi).
Thermal6
40CrNiMoA Q&T 38-42 HRC is rated for continuous service to 350°C (662 °F). It conducts heat at 44 W/m·K (25.4 BTU/hr·ft·°F), better than 57% of steel grades. Thermal expansion is 12.3 µm/m·K (6.83 µin/in·°F).
Electrical3
40CrNiMoA Q&T 38-42 HRC conducts electricity at 7 % IACS, worse than 74% of steel grades.
Chemical & Environmental3
Corrosion resistance is poor (15/100), better than 75% of steel grades.
Sustainability4
Producing a kilogram of 40CrNiMoA Q&T 38-42 HRC takes about 32 MJ of energy and emits 2.3 kg of CO₂ — more than 70% of steel grades. Typical recycled content is 30%.
Manufacturability8
40CrNiMoA Q&T 38-42 HRC's machinability is poor (30/100, worse than 89% of steel grades); weldability poor (30/100); formability poor (25/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 40CrNiMoA Q&T 38-42 HRC
Is 40CrNiMoA easy to machine?
Machine in the annealed or ≤32 HRC condition with rigid setups, sharp carbide and generous coolant; above 40 HRC switch to CBN/ceramic turning or grinding, and rough before final temper where possible.
Can 40CrNiMoA be welded?
High carbon equivalent means preheat 250–350 °C, low-hydrogen filler (e.g. ER100S/ER110S or matching), interpass control and immediate PWHT/re-temper; avoid welding parts already at high hardness.
Can 40CrNiMoA be formed, bent or molded?
Hot forge 1100–1200 °C, finish above 900 °C and normalize afterwards; cold forming is limited to the annealed condition and mild bends only.
What surface finishes work on 40CrNiMoA?
Not anodizable — protect with black oxide, phosphate + oil, Zn or Cd plating, hard chrome, or gas nitriding (surface 550–650 HV); bake 190–220 °C after electroplating high-hardness parts to relieve hydrogen.
40CrNiMoA 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 | 0.37 – 0.44 | 0.4 |
| Si | 0.17 – 0.37 | 0.27 |
| Mn | 0.5 – 0.8 | 0.65 |
| Cr | 0.6 – 0.9 | 0.75 |
| Ni | 1.25 – 1.65 | 1.45 |
| Mo | 0.15 – 0.25 | 0.2 |
| PA grade (high-quality) limit | ≤ 0.03 | |
| SA grade (high-quality) limit | ≤ 0.03 | |
| Curesidual | ≤ 0.3 | |
| Fe | balance |
40CrNiMoA Q&T 38-42 HRC — frequently asked
What is 40CrNiMoA Q&T 38-42 HRC used for?
40CrNiMoA Q&T 38-42 HRC is typically used for aircraft landing gear components, drive shafts, industrial axles, gearbox shafts and pinions, heavy-duty crankshafts and high-strength bolts and studs. In short: premium Ni-Cr-Mo bar.
What is the yield strength of 40CrNiMoA Q&T 38-42 HRC?
40CrNiMoA Q&T 38-42 HRC has a typical yield strength of 1,200 MPa (174 ksi) and a tensile strength of 1,300 MPa (189 ksi) — stronger than 94% of steel grades. Strength varies by condition: see the 10 listed tempers.
Is 40CrNiMoA Q&T 38-42 HRC easy to machine?
Not especially — machinability is rated poor (30/100, worse than 89% of steel grades). Machine in the annealed or ≤32 HRC condition with rigid setups, sharp carbide and generous coolant; above 40 HRC switch to CBN/ceramic turning or grinding, and rough before final temper where possible.
Can 40CrNiMoA Q&T 38-42 HRC be welded?
Not readily — weldability is rated poor (30/100). High carbon equivalent means preheat 250–350 °C, low-hydrogen filler (e.g. ER100S/ER110S or matching), interpass control and immediate PWHT/re-temper; avoid welding parts already at high hardness.
What surface finishes work on 40CrNiMoA Q&T 38-42 HRC?
Not anodizable — protect with black oxide, phosphate + oil, Zn or Cd plating, hard chrome, or gas nitriding (surface 550–650 HV); bake 190–220 °C after electroplating high-hardness parts to relieve hydrogen.
Can 40CrNiMoA Q&T 38-42 HRC be formed, bent or molded?
Hot forge 1100–1200 °C, finish above 900 °C and normalize afterwards; cold forming is limited to the annealed condition and mild bends only.
What is the maximum service temperature of 40CrNiMoA Q&T 38-42 HRC?
40CrNiMoA Q&T 38-42 HRC is rated for continuous use to about 350°C (662 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 40CrNiMoA Q&T and 40CrNiMoA-HR?
Q&T is the default condition — standard stocked condition: balanced ~1000–1100 MPa strength with high toughness for shafts, gears and high-strength fasteners. HR: cheapest mill condition, bought as forging or machining blank when the shop will heat treat afterwards; properties vary with section and cooling rate. Yield strength is 950 MPa in Q&T versus 620 MPa in HR.
Can FabDigit make parts in 40CrNiMoA Q&T 38-42 HRC?
Yes — 40CrNiMoA Q&T 38-42 HRC is available for CNC machining and sheet metal; every part is priced by an engineer rather than instantly. Upload a STEP file to get a price and a DFM check.
Sources
- GB/T 3077 Alloy structural steels (2015)
- ASTM A29/A29M and SAE J404 (4340) — ASTM / SAE (2020)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol.19 — Fatigue and Fracture — ASM International (1996)
- MMPDS-2023 typical properties for 4340 steel — Battelle/FAA (2023)
- Machinery's Handbook, 31st ed. (machinability ratings) — Industrial Press (2020)
- (40CrNiMoA) — Mysteel / 1688 (2025)
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.