Steel 42CD4 +QT (Quenched and tempered)
Heat-treated state · default condition
EN 42CD4 · AISI/SAE 4140
The standard stocked condition: general-purpose shafts, gears, bolts and tooling needing ~1000 MPa with good toughness.
Values for the +QT condition
Other 42CD4 tempers and conditions
42CD4 is listed in 17 conditions; see the grade overview at 42CD4.
- +S
- +A
- +FP
- +U
- +QT 100-250
- +N
- +C
- +QT 40-100
- QT 28-32 HRC
- Nitrided
- Induction Hardened
- +QT
- +QT ≤16
- QT 32-36 HRC
- QT 36-40 HRC
- QT 40-45 HRC
- QT 48-52 HRC
Compare all 17 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Treated to improve shearability | Soft, low-hardness bar for cold shearing of blanks before forging or heat treatment. | 400 | 640 | 24 | 11 HRC | 7.9 % IACS |
Annealed | Best condition for heavy machining, cold forming or deep drilling before final quench and temper. | 415 | 655 | 25 | 197 HB | — |
Treated to ferrite–pearlite structure and hardness range | Controlled soft structure specified when uniform machinability of bar stock matters more than strength. | 440 | 700 | 22 | 16 HRC | 8.4 % IACS |
Hot rolled | Cheapest mill delivery condition when the customer will heat treat the finished part anyway. | 560 | 900 | 16 | 25 HRC | 7.8 % IACS |
+QT, section 100–250 mm | Heavy forgings and large-diameter bar; core toughness stays good but strength drops with mass effect. | 560 | 850 | 17 | 25 HRC | 8 % IACS |
Normalized | Grain refinement and a uniform structure for forgings before machining or final hardening. | 655 | 1,020 | 18 | 32 HRC | — |
Cold drawn | Bright, close-tolerance bar for turned parts where a good surface and straightness are wanted before heat treatment. | 655 | 760 | 14 | 19 HRC | 7.8 % IACS |
+QT, section 40–100 mm | Medium shafts and forgings where mass effect lowers the core properties one class. | 700 | 950 | 15 | 29 HRC | 7.8 % IACS |
Q&T to 28–32 HRC | Common pre-hardened machining condition for shafts, hydraulic parts and mould bases. | 860 | 965 | 16 | 30 HRC | — |
Q&T + gas/plasma nitrided (case ≈0.3–0.6 mm, surface 550–650 HV) | Pick for wear and fatigue-critical shafts, spindles and gears where distortion must stay minimal. | 880 | 1,030 | 13 | 55 HRC | — |
Q&T core + induction-hardened surface (52–58 HRC case) | Selective surface hardening of journals, splines and cam tracks with a tough Q&T core. | 880 | 1,030 | 13 | 55 HRC | 7.5 % IACS |
+QTDefaultThis page Quenched and tempered | The standard stocked condition: general-purpose shafts, gears, bolts and tooling needing ~1000 MPa with good toughness. | 900 | 1,030 | 14 | 32 HRC | — |
+QT, section ≤16 mm | Thin bar/wire quenched right through, giving the highest EN 10083-3 property class. | 980 | 1,180 | 11 | 37 HRC | 7.5 % IACS |
Q&T to 32–36 HRC | Higher-strength pre-hard condition for gears, couplings and heavy-duty fasteners. | 1,000 | 1,100 | 14 | 34 HRC | — |
Q&T to 36–40 HRC | Chosen when wear resistance is wanted but through-hardened toughness must be retained. | 1,140 | 1,240 | 12 | 38 HRC | — |
Q&T to 40–45 HRC | High-strength condition for tooling, rock bits and highly loaded pins; machining needs carbide tooling. | 1,310 | 1,420 | 10 | 43 HRC | — |
Q&T low-temper to 48–52 HRC | Maximum hardness/wear resistance for small tools and dies; toughness and weldability are marginal. | 1,580 | 1,720 | 8 | 50 HRC | — |
What is 42CD4 +QT?
42CD4 +QT is 42CD4 heat treated to +QT — the standard stocked condition: general-purpose shafts, gears, bolts and tooling needing ~1000 MPa with good toughness. 42CD4 +QT has a yield strength of 900 MPa (131 ksi) and a tensile strength of 1,030 MPa (149 ksi) — stronger than 90% of steel grades. Elongation at break is 14% and the elastic modulus is 210 GPa (30.5 Msi). 42CD4 +QT 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).
Advantages
- High strength — 900 MPa (131 ksi), better than 90% of steel grades
- Polishes to a fine finish — 65/100, better than 78% of steel grades
Limitations
- Limited ductility — 14%, worse than 75% of steel grades
42CD4 +QT properties
Typical room-temperature values for 42CD4 +QT; 15 are specific to this condition. Other listed values are 42CD4 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
42CD4 +QT 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).
Mechanical16
42CD4 +QT has a yield strength of 900 MPa (131 ksi) and a tensile strength of 1,030 MPa (149 ksi) — stronger than 90% of steel grades. Elongation at break is 14% and the elastic modulus is 210 GPa (30.5 Msi).
Thermal6
42CD4 +QT is rated for continuous service to 400°C (752 °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
42CD4 +QT 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 42CD4 +QT takes about 34 MJ of energy and emits 2.3 kg of CO₂ — more than 82% of steel grades. Typical recycled content is 30%.
Manufacturability7
42CD4 +QT's machinability is fair (50/100, worse than 53% of steel grades); weldability fair (40/100); formability poor (30/100).
Common Calculations5
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 42CD4 +QT
Is 42CD4 easy to machine?
Machine in the annealed or 28–32 HRC pre-hard condition with coated carbide; above 40 HRC use CBN/ceramic or grind, and allow for higher cutting forces than mild steel.
Can 42CD4 be welded?
Weldable with low-hydrogen consumables but requires 250–350 °C preheat, controlled interpass and post-weld temper below the original tempering temperature to avoid HAZ cracking.
Can 42CD4 be formed, bent or molded?
Hot forge at 1100–850 °C then normalize; cold bending or heading only in the annealed condition, with generous bend radii.
What surface finishes work on 42CD4?
No anodizing; protect by black oxide, phosphating, zinc/Zn-Ni plating (bake at 200 °C to de-embrittle above 40 HRC), hard chrome or nitriding — all take a good polish.
42CD4 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 |
|---|---|---|
| CEN 10083-3 / NF A35-552 | 0.38 – 0.45 | 0.42 |
| Si | ≤ 0.4 | 0.25 |
| Mn | 0.6 – 0.9 | 0.75 |
| P | ≤ 0.03 | 0.02 |
| S0.020–0.040 for free-machining variant 42CrMoS4 | ≤ 0.04 | 0.02 |
| Cr | 0.9 – 1.2 | 1.05 |
| Mo | 0.15 – 0.3 | 0.22 |
| Fe | balance | — |
42CD4 +QT — frequently asked
What is 42CD4 +QT used for?
42CD4 +QT is typically used for shafts, gears, tooling and fasteners. In short: benchmark Cr-Mo shaft steel; widest range of tempers; higher strength than 35CD4.
What is the yield strength of 42CD4 +QT?
42CD4 +QT has a typical yield strength of 900 MPa (131 ksi) and a tensile strength of 1,030 MPa (149 ksi) — stronger than 90% of steel grades. Strength varies by condition: see the 17 listed tempers.
Is 42CD4 +QT easy to machine?
Reasonably — machinability is rated fair (50/100, worse than 53% of steel grades). Machine in the annealed or 28–32 HRC pre-hard condition with coated carbide; above 40 HRC use CBN/ceramic or grind, and allow for higher cutting forces than mild steel.
Can 42CD4 +QT be welded?
With care — weldability is rated fair (40/100). Weldable with low-hydrogen consumables but requires 250–350 °C preheat, controlled interpass and post-weld temper below the original tempering temperature to avoid HAZ cracking.
What surface finishes work on 42CD4 +QT?
No anodizing; protect by black oxide, phosphating, zinc/Zn-Ni plating (bake at 200 °C to de-embrittle above 40 HRC), hard chrome or nitriding — all take a good polish.
Can 42CD4 +QT be formed, bent or molded?
Hot forge at 1100–850 °C then normalize; cold bending or heading only in the annealed condition, with generous bend radii.
What is the maximum service temperature of 42CD4 +QT?
42CD4 +QT 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.
Sources
- EN 10083-3 Steels for quenching and tempering – Alloy steels — CEN (2006)
- NF A35-552 / AFNOR designation 42CD4 — AFNOR (1993)
- SAE J404 Chemical Compositions of SAE Alloy Steels (4140) — SAE International (2021)
- GB/T 3077 (42CrMo) — SAC (2015)
- 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)
- 42CrMo4 / 1.7225 quenched and tempered steel datasheet — Ovako / Böhler (2022)
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.