Steel 35CD4 +QT-heavy (+QT heavy section)
Heat-treated state
EN 35CD4 · AISI/SAE 4135
Use for large forgings and thick bar where hardenability limits the achievable strength.
Values for the +QT-heavy condition
Other 35CD4 tempers and conditions
35CD4 is listed in 12 conditions; see the grade overview at 35CD4.
Compare all 12 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Spheroidize annealed | Choose when the part is cold headed, cold extruded or deep machined before hardening. | 350 | 560 | 26 | 175 HB | 8 % IACS |
Annealed | Delivery condition for heavy machining, cold forming or before final heat treatment. | 400 | 620 | 22 | 200 HB | — |
Hot rolled | Cheapest mill condition; buy when the part will be fully heat treated after rough machining. | 440 | 700 | 18 | 17 HRC | 8 % IACS |
Normalized | Uniform fine-grain structure for weldments and parts that will not be quenched. | 480 | 750 | 18 | 20 HRC | — |
+QT-heavyThis page +QT heavy section | Use for large forgings and thick bar where hardenability limits the achievable strength. | 540 | 820 | 16 | 23 HRC | 8 % IACS |
Cold drawn | Pick for close-tolerance bright bar where the extra 15–20 % strength from drawing is enough. | 560 | 720 | 12 | 18 HRC | 8 % IACS |
Q&T to 22–26 HRC | Specify when H2S sulphide-stress-cracking rules cap hardness at 22 HRC max plus margin. | 620 | 800 | 18 | 24 HRC | 8 % IACS |
+QTDefault Quenched and tempered | Standard stocked condition for shafts, gears and highly loaded bolting; best strength/toughness balance. | 700 | 950 | 14 | 29 HRC | — |
Q&T + gas/plasma nitrided case | Choose for wear and fatigue-critical shafts; core keeps Q&T properties while the case reaches ~600 HV. | 700 | 950 | 14 | 56 HRC | 8 % IACS |
Q&T to 28–32 HRC | Common hardness call-out for machined shafts, couplings and pressure parts. | 780 | 960 | 15 | 30 HRC | 8 % IACS |
+QT thin section | Highest strength class of the grade, only achievable in small diameters and thin walls. | 850 | 1,080 | 12 | 35 HRC | 8 % IACS |
Q&T to 32–36 HRC | Upper practical hardness for this carbon level; use for wear-loaded shafts and high-strength fasteners. | 900 | 1,100 | 12 | 34 HRC | 8 % IACS |
What is 35CD4 +QT-heavy?
35CD4 +QT-heavy is 35CD4 heat treated to +QT-heavy — use for large forgings and thick bar where hardenability limits the achievable strength. 35CD4 +QT-heavy has a yield strength of 540 MPa (78.3 ksi) and a tensile strength of 820 MPa (119 ksi) — stronger than 70% of steel grades. Elongation at break is 16% and the elastic modulus is 210 GPa (30.5 Msi). 35CD4 +QT-heavy 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-heavy is available on request or by drawing note.
Advantages
- High service temperature — 450°C (842 °F), better than 86% of steel grades
- Polishes to a fine finish — 65/100, better than 78% of steel grades
35CD4 +QT-heavy properties
Typical room-temperature values for 35CD4 +QT-heavy; 23 are specific to this condition. Other listed values are 35CD4 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
35CD4 +QT-heavy 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
35CD4 +QT-heavy has a yield strength of 540 MPa (78.3 ksi) and a tensile strength of 820 MPa (119 ksi) — stronger than 70% of steel grades. Elongation at break is 16% and the elastic modulus is 210 GPa (30.5 Msi).
Thermal6
35CD4 +QT-heavy is rated for continuous service to 450°C (842 °F). It conducts heat at 43 W/m·K (24.8 BTU/hr·ft·°F), better than 51% of steel grades. Thermal expansion is 12.3 µm/m·K (6.83 µin/in·°F).
Electrical3
35CD4 +QT-heavy conducts electricity at 8 % IACS, better than 55% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of 35CD4 +QT-heavy takes about 33 MJ of energy and emits 2.3 kg of CO₂ — more than 76% of steel grades. Typical recycled content is 30%.
Manufacturability6
35CD4 +QT-heavy's machinability is good (58/100, better than 75% of steel grades); weldability fair (45/100); formability poor (28/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 35CD4 +QT-heavy
Is 35CD4 easy to machine?
Machine in the annealed or ≤300 HB Q&T state with rigid setups, coated carbide, ~120–180 m/min turning; above 34 HRC switch to CBN or grinding.
Can 35CD4 be welded?
Weldable with low-hydrogen consumables but preheat 200–300 °C and stress relieve/temper at 550–650 °C after welding to avoid HAZ cracking; CE ≈ 0.75.
Can 35CD4 be formed, bent or molded?
Hot forge 1100–850 °C then normalize; cold form only in the +A/+AC spheroidized condition, otherwise bend hot or with generous radii.
What surface finishes work on 35CD4?
No anodizing (ferrous); protect by zinc/Cr plating, manganese phosphate, black oxide, nitriding or paint — bake after plating to avoid hydrogen embrittlement above 30 HRC.
35CD4 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 | 0.3 – 0.37 | 0.34 |
| Si | ≤ 0.4 | 0.25 |
| Mn | 0.6 – 0.9 | 0.75 |
| P0.035 max in some product standards | ≤ 0.03 | — |
| S≤0.005 for +S/free-cutting or ≤0.010 for clean variants | ≤ 0.04 | — |
| Cr | 0.9 – 1.2 | 1.05 |
| Mo | 0.15 – 0.3 | 0.22 |
| Fe | balance | — |
35CD4 +QT-heavy — frequently asked
What is 35CD4 +QT-heavy used for?
35CD4 +QT-heavy is typically used for shafts, connecting rods and structural parts. In short: weldable Cr-Mo grade; lower carbon than 42CD4; good medium-strength shaft steel.
What is the yield strength of 35CD4 +QT-heavy?
35CD4 +QT-heavy has a typical yield strength of 540 MPa (78.3 ksi) and a tensile strength of 820 MPa (119 ksi) — stronger than 70% of steel grades. Strength varies by condition: see the 12 listed tempers.
Is 35CD4 +QT-heavy easy to machine?
Reasonably — machinability is rated good (58/100, better than 75% of steel grades). Machine in the annealed or ≤300 HB Q&T state with rigid setups, coated carbide, ~120–180 m/min turning; above 34 HRC switch to CBN or grinding.
Can 35CD4 +QT-heavy be welded?
With care — weldability is rated fair (45/100). Weldable with low-hydrogen consumables but preheat 200–300 °C and stress relieve/temper at 550–650 °C after welding to avoid HAZ cracking; CE ≈ 0.75.
What surface finishes work on 35CD4 +QT-heavy?
No anodizing (ferrous); protect by zinc/Cr plating, manganese phosphate, black oxide, nitriding or paint — bake after plating to avoid hydrogen embrittlement above 30 HRC.
Can 35CD4 +QT-heavy be formed, bent or molded?
Hot forge 1100–850 °C then normalize; cold form only in the +A/+AC spheroidized condition, otherwise bend hot or with generous radii.
What is the maximum service temperature of 35CD4 +QT-heavy?
35CD4 +QT-heavy is rated for continuous use to about 450°C (842 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 35CD4 +QT and 35CD4-HR?
+QT is the default condition — standard stocked condition for shafts, gears and highly loaded bolting; best strength/toughness balance. HR: cheapest mill condition; buy when the part will be fully heat treated after rough machining. Yield strength is 700 MPa in +QT versus 440 MPa in HR.
Sources
- EN 10083-3 Steels for quenching and tempering — Alloy steels (34CrMo4 / 1.7220) — CEN (2006)
- NF A35-552 / AFNOR 35CD4 alloy structural steel — AFNOR (1993)
- GB/T 3077 (35CrMo) — SAC (2015)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol.16 Machining / Vol.19 Fatigue and Fracture — ASM International (1996)
- 1.7220 / 34CrMo4 hot-rolled and Q&T bar datasheet — European long-products mill (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.