Steel 40CrNi QT-38-42HRC
Hardness band
GB 40CrNi
Maximum practical Q&T hardness for this grade — high wear resistance, reduced impact energy and machinability.
Values for the QT-38-42HRC condition
Other 40CrNi tempers and conditions
40CrNi is listed in 11 conditions; see the grade overview at 40CrNi.
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 forming or before final quench and temper. | 420 | 690 | 21 | 200 HB | — |
Hot rolled | Mill as-rolled bar bought for subsequent forging or full heat treatment by the user. | 480 | 780 | 16 | 230 HB | — |
Normalized | Grain refinement and uniform structure after forging; used when full Q&T strength is not required. | 540 | 850 | 18 | 23 HRC | 7.8 % IACS |
Cold drawn | Bright, close-tolerance bar for parts machined without further heat treatment. | 680 | 830 | 11 | 245 HB | — |
Q&T 25–30 HRC (high-temperature temper ~600 °C) | Toughest Q&T level; pick for large sections, welded-then-tempered parts or heavy shock loading. | 780 | 930 | 16 | 28 HRC | — |
QTDefault Quenched and tempered | Standard delivery condition — oil quenched from 820 °C and tempered at 500 °C to GB/T 3077 — giving 840 MPa yield, ~1020 MPa tensile and ≥55 J impact for shafts, gears and rods. | 840 | 1,020 | 12 | 31 HRC | — |
Q&T core with induction-hardened surface (52–58 HRC case) | Choose for journals, spline and gear tooth flanks needing wear resistance and compressive residual stress on a tough core. | 840 | 1,020 | 11 | 55 HRC | 7.3 % IACS |
Q&T 30–34 HRC (temper ~540 °C) | Balanced strength/toughness hardness band commonly specified for gear blanks and drive shafts. | 880 | 1,050 | 14 | 32 HRC | — |
Q&T 34–38 HRC (temper ~480 °C) | Higher-strength band for high-load bolts, rods and small-section shafts where toughness margin is lower. | 1,030 | 1,180 | 12 | 36 HRC | — |
QT-38-42HRCThis page Q&T 38–42 HRC (temper ~400 °C) | Maximum practical Q&T hardness for this grade — high wear resistance, reduced impact energy and machinability. | 1,180 | 1,330 | 10 | 40 HRC | — |
As-quenched | Intermediate state only — must be tempered immediately; quoted for hardenability/hardness checks. | 1,550 | 2,000 | 2 | 55 HRC | 6.5 % IACS |
What is 40CrNi QT-38-42HRC?
40CrNi QT-38-42HRC is 40CrNi heat treated to QT-38-42HRC — maximum practical Q&T hardness for this grade — high wear resistance, reduced impact energy and machinability. 40CrNi QT-38-42HRC has a yield strength of 1,180 MPa (171 ksi) and a tensile strength of 1,330 MPa (193 ksi) — stronger than 94% of steel grades. Elongation at break is 10% and the elastic modulus is 210 GPa (30.5 Msi). 40CrNi QT-38-42HRC 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; QT-38-42HRC is available on request or by drawing note.
Advantages
- High strength — 1,180 MPa (171 ksi), better than 94% of steel grades
- Polishes to a fine finish — 65/100, better than 78% of steel grades
Limitations
- Limited ductility — 10%, worse than 91% of steel grades
- Difficult to machine — 32/100, worse than 87% of steel grades
- Limited service temperature — 300°C (572 °F), worse than 78% of steel grades
40CrNi QT-38-42HRC properties
Typical room-temperature values for 40CrNi QT-38-42HRC; 12 are specific to this condition. Other listed values are 40CrNi reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
40CrNi QT-38-42HRC 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
40CrNi QT-38-42HRC has a yield strength of 1,180 MPa (171 ksi) and a tensile strength of 1,330 MPa (193 ksi) — stronger than 94% of steel grades. Elongation at break is 10% and the elastic modulus is 210 GPa (30.5 Msi).
Thermal6
40CrNi QT-38-42HRC is rated for continuous service to 300°C (572 °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
40CrNi QT-38-42HRC conducts electricity at 7.5 % IACS, worse than 67% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of 40CrNi QT-38-42HRC takes about 26 MJ of energy and emits 2 kg of CO₂ — less than 64% of steel grades. Typical recycled content is 30%.
Manufacturability7
40CrNi QT-38-42HRC's machinability is poor (32/100, worse than 87% 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 40CrNi QT-38-42HRC
Is 40CrNi easy to machine?
Best machined annealed (≤250 HB) or after tempering to 28–32 HRC; use rigid setups, coated carbide, 80–140 m/min, and expect ~50 % of 1212 free-cutting rate.
Can 40CrNi be welded?
Poor weldability (CE ≈ 0.85): preheat 250–350 °C, low-hydrogen electrodes, and temper immediately after welding; avoid welding on fully hardened parts.
Can 40CrNi be formed, bent or molded?
Hot forge 1150–850 °C then slow cool/anneal; cold bending or upsetting only in the annealed state with generous radii.
What surface finishes work on 40CrNi?
Not corrosion resistant — protect with black oxide, phosphate + oil, zinc or hard chrome plating (bake at 190 °C for hydrogen relief); nitriding or induction hardening adds wear resistance.
40CrNi 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 3077-2015 | 0.37 – 0.44 | 0.4 |
| Si | 0.17 – 0.37 | 0.27 |
| Mn | 0.5 – 0.8 | 0.65 |
| Cr | 0.45 – 0.75 | 0.6 |
| Ni | 1 – 1.4 | 1.2 |
| P | ≤ 0.04 | 0.02 |
| S | ≤ 0.04 | 0.02 |
| Curesidual, max | ≤ 0.3 | 0.15 |
| Fe | balance | — |
40CrNi QT-38-42HRC — frequently asked
What is 40CrNi QT-38-42HRC used for?
40CrNi QT-38-42HRC is typically used for shafts, gears, connecting rods and bolts. In short: tougher than 40Cr; deep-hardening Ni-Cr grade; limited stock availability.
What is the yield strength of 40CrNi QT-38-42HRC?
40CrNi QT-38-42HRC has a typical yield strength of 1,180 MPa (171 ksi) and a tensile strength of 1,330 MPa (193 ksi) — stronger than 94% of steel grades. Strength varies by condition: see the 11 listed tempers.
Is 40CrNi QT-38-42HRC easy to machine?
Not especially — machinability is rated poor (32/100, worse than 87% of steel grades). Best machined annealed (≤250 HB) or after tempering to 28–32 HRC; use rigid setups, coated carbide, 80–140 m/min, and expect ~50 % of 1212 free-cutting rate.
Can 40CrNi QT-38-42HRC be welded?
Not readily — weldability is rated poor (30/100). Poor weldability (CE ≈ 0.85): preheat 250–350 °C, low-hydrogen electrodes, and temper immediately after welding; avoid welding on fully hardened parts.
What surface finishes work on 40CrNi QT-38-42HRC?
Not corrosion resistant — protect with black oxide, phosphate + oil, zinc or hard chrome plating (bake at 190 °C for hydrogen relief); nitriding or induction hardening adds wear resistance.
Can 40CrNi QT-38-42HRC be formed, bent or molded?
Hot forge 1150–850 °C then slow cool/anneal; cold bending or upsetting only in the annealed state with generous radii.
What is the maximum service temperature of 40CrNi QT-38-42HRC?
40CrNi QT-38-42HRC is rated for continuous use to about 300°C (572 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 40CrNi-QT and 40CrNi-Q?
QT is the default condition — standard delivery condition — oil quenched from 820 °C and tempered at 500 °C to GB/T 3077 — giving 840 MPa yield, ~1020 MPa tensile and ≥55 J impact for shafts, gears and rods. Q: intermediate state only — must be tempered immediately; quoted for hardenability/hardness checks. Yield strength is 840 MPa in QT versus 1,550 MPa in Q.
Sources
- GB/T 3077 Alloy structural steels — SAC (China) (2015)
- SAE J404 / AISI 3140 chemical composition — SAE International (2009)
- 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)
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.