Steel C35 +QT100 (+QT)
Heat-treated state
EN C35 · AISI/SAE 1035 · JIS S35C · GB 35
Heavy Q&T sections; low hardenability of C35 limits core strength, so properties approach normalized values.
Values for the +QT100 condition
Other C35 tempers and conditions
C35 is listed in 9 conditions; see the grade overview at C35.
Compare all 9 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Annealed | Softest condition — pick for cold forming, deep machining or before further heat treatment. | 275 | 520 | 25 | 155 HB | — |
Hot rolled | Cheapest stock condition for non-critical parts that will be machined or later heat treated. | 300 | 560 | 20 | 160 HB | — |
Treated to ferrite–pearlite structure and hardness range | Supply condition specified when consistent machinability and a controlled hardness band are required. | 310 | 580 | 21 | 170 HB | 10.5 % IACS |
+NDefault Normalized | Default stock condition: uniform fine grain, balanced strength/toughness for general shafts and machined parts. | 320 | 600 | 20 | 175 HB | — |
+QT100This page +QT | Heavy Q&T sections; low hardenability of C35 limits core strength, so properties approach normalized values. | 350 | 620 | 20 | 185 HB | 10.5 % IACS |
+QT | Standard commercial Q&T bar size range for machine shafts and couplings. | 410 | 670 | 19 | 16 HRC | — |
Induction hardened | Pick when a wear-resistant, compressively stressed surface is needed on a tough Q&T shaft (journals, splines, rack teeth). | 450 | 700 | 15 | 54 HRC | 9.5 % IACS |
+QT | Highest strength condition for small-diameter shafts, bolts and pins where full through-hardening is possible. | 460 | 700 | 18 | 19 HRC | — |
Cold drawn | Choose for tight tolerance, good surface bright bar and higher yield without heat treatment; ductility is reduced. | 530 | 650 | 11 | 200 HB | — |
What is C35 +QT100?
C35 +QT100 is C35 heat treated to +QT100 — heavy Q&T sections; low hardenability of C35 limits core strength, so properties approach normalized values. C35 +QT100 has a yield strength of 350 MPa (50.8 ksi) and a tensile strength of 620 MPa (89.9 ksi) — weaker than 74% of steel grades. Elongation at break is 20% and the elastic modulus is 210 GPa (30.5 Msi). C35 +QT100 has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,425°C (2,597 °F). +N is the default condition FabDigit quotes; +QT100 is available on request or by drawing note.
Advantages
- High electrical conductivity — 10.5 % IACS, better than 89% of steel grades
- Conducts heat well — 48 W/m·K (27.7 BTU/hr·ft·°F), better than 79% of steel grades
Limitations
- Low fracture toughness — 60 MPa·√m (54.6 ksi·√in), worse than 78% of steel grades
C35 +QT100 properties
Typical room-temperature values for C35 +QT100; 22 are specific to this condition. Other listed values are C35 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
C35 +QT100 has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,425°C (2,597 °F).
Mechanical16
C35 +QT100 has a yield strength of 350 MPa (50.8 ksi) and a tensile strength of 620 MPa (89.9 ksi) — weaker than 74% of steel grades. Elongation at break is 20% and the elastic modulus is 210 GPa (30.5 Msi).
Thermal6
C35 +QT100 is rated for continuous service to 400°C (752 °F). It conducts heat at 48 W/m·K (27.7 BTU/hr·ft·°F), better than 79% of steel grades. Thermal expansion is 11.5 µm/m·K (6.39 µin/in·°F).
Electrical3
C35 +QT100 conducts electricity at 10.5 % IACS, better than 89% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (10/100), worse than 86% of steel grades.
Sustainability4
Producing a kilogram of C35 +QT100 takes about 25 MJ of energy and emits 2.1 kg of CO₂ — less than 82% of steel grades. Typical recycled content is 25%.
Manufacturability7
C35 +QT100's machinability is fair (54/100, better than 54% of steel grades); weldability fair (45/100); formability fair (35/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with C35 +QT100
Is C35 easy to machine?
Machines well in normalized or cold-drawn condition (~65 % of 1212); use carbide at 120–180 m/min, expect stringy chips in annealed stock — a chip breaker or slight cold work helps.
Can C35 be welded?
Weldable but carbon equivalent ≈0.48 — preheat 150–250 °C for sections over ~20 mm, use low-hydrogen consumables and stress relieve or re-normalize after welding.
Can C35 be formed, bent or molded?
Hot forge/roll at 1100–850 °C then normalize; cold bending is limited by low ductility — anneal first and use generous bend radii.
What surface finishes work on C35?
No natural corrosion protection: zinc/nickel plating, phosphating, black oxide, or paint; polishes to a fair finish but nitriding/induction hardening are preferred for wear surfaces.
C35 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 | 0.32 – 0.39 | 0.35 |
| Si | ≤ 0.4 | 0.25 |
| Mn | 0.5 – 0.8 | 0.65 |
| PC35E ≤0.030, C35R ≤0.030 | ≤ 0.05 | — |
| SC35E ≤0.035; C35R 0.020–0.040 | ≤ 0.05 | — |
| Crresidual | ≤ 0.4 | — |
| Niresidual | ≤ 0.4 | — |
| Moresidual | ≤ 0.1 | — |
| Cr+Mo+Nisum of residual elements | ≤ 0.63 | — |
| Fe | balance | — |
C35 +QT100 — frequently asked
What is C35 +QT100 used for?
C35 +QT100 is typically used for shafts, bolts, gears, machine parts and forged components. In short: mid-range carbon shaft steel; heat-treatable to 600 MPa; cheaper than alloy steel.
What is the yield strength of C35 +QT100?
C35 +QT100 has a typical yield strength of 350 MPa (50.8 ksi) and a tensile strength of 620 MPa (89.9 ksi) — weaker than 74% of steel grades. Strength varies by condition: see the 9 listed tempers.
Is C35 +QT100 easy to machine?
Reasonably — machinability is rated fair (54/100, better than 54% of steel grades). Machines well in normalized or cold-drawn condition (~65 % of 1212); use carbide at 120–180 m/min, expect stringy chips in annealed stock — a chip breaker or slight cold work helps.
Can C35 +QT100 be welded?
With care — weldability is rated fair (45/100). Weldable but carbon equivalent ≈0.48 — preheat 150–250 °C for sections over ~20 mm, use low-hydrogen consumables and stress relieve or re-normalize after welding.
What surface finishes work on C35 +QT100?
No natural corrosion protection: zinc/nickel plating, phosphating, black oxide, or paint; polishes to a fair finish but nitriding/induction hardening are preferred for wear surfaces.
Can C35 +QT100 be formed, bent or molded?
Hot forge/roll at 1100–850 °C then normalize; cold bending is limited by low ductility — anneal first and use generous bend radii.
What is the maximum service temperature of C35 +QT100?
C35 +QT100 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.
What is the difference between C35 +N and C35-IH?
+N is the default condition — default stock condition: uniform fine grain, balanced strength/toughness for general shafts and machined parts. IH: pick when a wear-resistant, compressively stressed surface is needed on a tough Q&T shaft (journals, splines, rack teeth). Yield strength is 320 MPa in +N versus 450 MPa in IH.
Sources
- EN 10083-2 — Steels for quenching and tempering: non-alloy steels — CEN (2006)
- EN 10277-2 — Bright steel products: general engineering steels — CEN (2008)
- JIS G 4051 — Carbon steels for machine structural use (S35C) — JISC (2016)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol.4 — Heat Treating — ASM International (1991)
- Mysteel / SMM (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.