Steel 35CrMnSiA-QT300
Heat-treated state
GB 35CrMnSiA
QT300 = q&T
Slight strength trade for better ductility; avoid dwelling at 300–400 °C where temper embrittlement is worst.
Values for the QT300 condition
Other 35CrMnSiA tempers and conditions
35CrMnSiA is listed in 8 conditions; see the grade overview at 35CrMnSiA.
Compare all 8 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Solution annealed | Choose for machining, cold sawing and blank preparation before final quench-and-temper. | 450 | 720 | 18 | 215 HB | — |
Hot rolled | Mill supply condition for bar and billet to be re-heat-treated by the user; hard and stringy, not a service condition. | 620 | 900 | 13 | 30 HRC | 7.5 % IACS |
Normalized | Grain refinement and structure homogenisation of forgings before final hardening; also used for moderately loaded parts. | 700 | 950 | 14 | 31 HRC | 7.5 % IACS |
Cold drawn | Small-diameter bright bar for parts machined to size before hardening; tighter tolerance, higher as-supplied strength. | 720 | 880 | 9 | 27 HRC | 7.5 % IACS |
Q&T | Toughest quench-and-temper level, for parts that must be machined after heat treatment or see impact loading. | 950 | 1,100 | 15 | 34 HRC | — |
Q&T | Balanced condition around 40 HRC for heavily loaded shafts and connecting rods needing more toughness than the 230 °C temper. | 1,150 | 1,300 | 13 | 40 HRC | — |
QT300This page Q&T | Slight strength trade for better ductility; avoid dwelling at 300–400 °C where temper embrittlement is worst. | 1,330 | 1,550 | 11 | 45 HRC | 6.5 % IACS |
QT230Default Q&T | The GB/T 3077 specification condition — maximum strength (≥1620 MPa) for landing-gear fittings, high-strength bolts and rocket structures. | 1,400 | 1,700 | 10 | 48 HRC | — |
What is 35CrMnSiA-QT300?
35CrMnSiA-QT300 is 35CrMnSiA heat treated to QT300 — slight strength trade for better ductility; avoid dwelling at 300–400 °C where temper embrittlement is worst. 35CrMnSiA-QT300 has a yield strength of 1,330 MPa (193 ksi) and a tensile strength of 1,550 MPa (225 ksi) — stronger than 95% of steel grades. Elongation at break is 11% and the elastic modulus is 205 GPa (29.7 Msi). 35CrMnSiA-QT300 has a density of 7.82 g/cm³ (0.283 lb/in³), lighter than 82% of steel grades. It melts at 1,420°C (2,588 °F). QT230 is the default condition FabDigit quotes; QT300 is available on request or by drawing note.
Advantages
- High strength — 1,330 MPa (193 ksi), better than 95% of steel grades
- Polishes to a fine finish — 75/100, better than 94% of steel grades
Limitations
- Limited formability — 12/100, worse than 92% of steel grades
- Limited ductility — 11%, worse than 89% of steel grades
- Difficult to machine — 32/100, worse than 87% of steel grades
- Low fracture toughness — 50 MPa·√m (45.5 ksi·√in), worse than 86% of steel grades
- Limited service temperature — 250°C (482 °F), worse than 85% of steel grades
35CrMnSiA-QT300 properties
Typical room-temperature values for 35CrMnSiA-QT300; 22 are specific to this condition. Other listed values are 35CrMnSiA reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
35CrMnSiA-QT300 has a density of 7.82 g/cm³ (0.283 lb/in³), lighter than 82% of steel grades. It melts at 1,420°C (2,588 °F).
Mechanical16
35CrMnSiA-QT300 has a yield strength of 1,330 MPa (193 ksi) and a tensile strength of 1,550 MPa (225 ksi) — stronger than 95% of steel grades. Elongation at break is 11% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
35CrMnSiA-QT300 is rated for continuous service to 250°C (482 °F). It conducts heat at 36 W/m·K (20.8 BTU/hr·ft·°F), worse than 73% of steel grades. Thermal expansion is 11.5 µm/m·K (6.39 µin/in·°F).
Electrical2
35CrMnSiA-QT300 has an electrical resistivity of 2.65×10⁻⁷ Ω·m.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of 35CrMnSiA-QT300 takes about 29 MJ of energy and emits 2.3 kg of CO₂ — less than 53% of steel grades. Typical recycled content is 25%.
Manufacturability7
35CrMnSiA-QT300's machinability is poor (32/100, worse than 87% of steel grades); weldability poor (20/100); formability not recommended (12/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 35CrMnSiA-QT300
Is 35CrMnSiA easy to machine?
Machine in the annealed (≤229 HB) state with carbide tools; at 45–50 HRC only finish grinding, hard turning with CBN or EDM is practical.
Can 35CrMnSiA be welded?
Poor weldability — high carbon plus 1.2 % Si gives crack-prone HAZ; if unavoidable use 200–350 °C preheat, low-hydrogen filler, and immediate post-weld temper at the part's temper temperature.
Can 35CrMnSiA be formed, bent or molded?
Hot forge 1150–850 °C with slow cooling or immediate anneal; cold forming only in the annealed condition and with generous bend radii.
What surface finishes work on 35CrMnSiA?
Grind then zinc, cadmium or Zn-Ni plate, phosphate or prime-and-paint; bake at 190–200 °C for ≥4 h after plating/pickling to relieve hydrogen embrittlement, and shot-peen fillets to restore fatigue life.
35CrMnSiA 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 | 0.32 – 0.39 | 0.35 |
| Siraises temper resistance and hardenability | 1.1 – 1.4 | 1.25 |
| Mn | 0.8 – 1.1 | 0.95 |
| Cr | 1.1 – 1.4 | 1.25 |
| PA = high-grade quality steel, low P/S | ≤ 0.03 | — |
| S | ≤ 0.03 | — |
| Niresidual | ≤ 0.3 | — |
| Curesidual | ≤ 0.25 | — |
| Fe | balance | — |
35CrMnSiA-QT300 — frequently asked
What is 35CrMnSiA-QT300 used for?
35CrMnSiA-QT300 is typically used for aircraft structural parts, high-strength fasteners and shafts. In short: very high strength after Q&T; crack-prone HAZ; aircraft structural grade.
What is the yield strength of 35CrMnSiA-QT300?
35CrMnSiA-QT300 has a typical yield strength of 1,330 MPa (193 ksi) and a tensile strength of 1,550 MPa (225 ksi) — stronger than 95% of steel grades. Strength varies by condition: see the 8 listed tempers.
Is 35CrMnSiA-QT300 easy to machine?
Not especially — machinability is rated poor (32/100, worse than 87% of steel grades). Machine in the annealed (≤229 HB) state with carbide tools; at 45–50 HRC only finish grinding, hard turning with CBN or EDM is practical.
Can 35CrMnSiA-QT300 be welded?
Not readily — weldability is rated poor (20/100). Poor weldability — high carbon plus 1.2 % Si gives crack-prone HAZ; if unavoidable use 200–350 °C preheat, low-hydrogen filler, and immediate post-weld temper at the part's temper temperature.
What surface finishes work on 35CrMnSiA-QT300?
Grind then zinc, cadmium or Zn-Ni plate, phosphate or prime-and-paint; bake at 190–200 °C for ≥4 h after plating/pickling to relieve hydrogen embrittlement, and shot-peen fillets to restore fatigue life.
Can 35CrMnSiA-QT300 be formed, bent or molded?
Hot forge 1150–850 °C with slow cooling or immediate anneal; cold forming only in the annealed condition and with generous bend radii.
What is the maximum service temperature of 35CrMnSiA-QT300?
35CrMnSiA-QT300 is rated for continuous use to about 250°C (482 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 35CrMnSiA-QT230 and 35CrMnSiA-A?
QT230 is the default condition — the GB/T 3077 specification condition — maximum strength (≥1620 MPa) for landing-gear fittings, high-strength bolts and rocket structures. A: choose for machining, cold sawing and blank preparation before final quench-and-temper. Yield strength is 1,400 MPa in QT230 versus 450 MPa in A.
Sources
- ASM Handbook Vol. 1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
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.