Steel 30CrMnSiA QT35-40HRC
Hardness band
GB 30CrMnSiA
Higher-strength Q&T level (~1200 MPa) for landing-gear links, lugs and highly loaded bolts.
Values for the QT35-40HRC condition
Other 30CrMnSiA tempers and conditions
30CrMnSiA is listed in 10 conditions; see the grade overview at 30CrMnSiA.
Compare all 10 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Solution annealed | Softest condition — choose for deep machining, cold forming or tube bending before final heat treatment. | 420 | 700 | 20 | 215 HB | — |
Hot rolled | Mill supply condition for bar and plate that will be machined then heat treated by the user. | 480 | 780 | 16 | 23 HRC | 7.5 % IACS |
Stress relieved | Typical delivery state for welded 30CrMnSiA tube frames before final Q&T or for moderate-load weldments. | 500 | 750 | 18 | 21 HRC | 7.5 % IACS |
Normalized | Uniform fine-grain structure for forgings and pre-machining stability before Q&T. | 540 | 830 | 15 | 25 HRC | 7.4 % IACS |
Cold drawn | Close-tolerance bright bar for shafts and fasteners machined without further heat treatment. | 720 | 880 | 10 | 27 HRC | 7.3 % IACS |
Q&T 28–32 HRC (temper ~570 °C) | Tough, machinable condition for shafts and general aerospace hardware where 900–1000 MPa suffices. | 800 | 960 | 16 | 30 HRC | — |
QT1080Default Q&T | Standard GB/T 3077 delivery condition — best balance of 1100 MPa strength and toughness for structural parts. | 930 | 1,130 | 12 | 36 HRC | — |
QT35-40HRCThis page Q&T 35–40 HRC (temper ~450–500 °C) | Higher-strength Q&T level (~1200 MPa) for landing-gear links, lugs and highly loaded bolts. | 1,080 | 1,230 | 11 | 38 HRC | — |
Q&T high strength | Aerospace high-strength condition for thin-wall welded structures and fittings; toughness and hydrogen-embrittlement margin drop sharply. | 1,350 | 1,560 | 8 | 46 HRC | — |
As-quenched | Intermediate process condition only; must be tempered promptly to avoid quench cracking. | 1,350 | 1,800 | 3 | 51 HRC | 6.5 % IACS |
What is 30CrMnSiA QT35-40HRC?
30CrMnSiA QT35-40HRC is 30CrMnSiA heat treated to QT35-40HRC — higher-strength Q&T level (~1200 MPa) for landing-gear links, lugs and highly loaded bolts. 30CrMnSiA QT35-40HRC has a yield strength of 1,080 MPa (157 ksi) and a tensile strength of 1,230 MPa (178 ksi) — stronger than 93% of steel grades. Elongation at break is 11% and the elastic modulus is 210 GPa (30.5 Msi). 30CrMnSiA QT35-40HRC 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). QT1080 is the default condition FabDigit quotes; QT35-40HRC is available on request or by drawing note.
Advantages
- High strength — 1,080 MPa (157 ksi), better than 93% of steel grades
- Polishes to a fine finish — 65/100, better than 78% of steel grades
Limitations
- Limited ductility — 11%, worse than 89% of steel grades
- Difficult to machine — 36/100, worse than 81% of steel grades
30CrMnSiA QT35-40HRC properties
Typical room-temperature values for 30CrMnSiA QT35-40HRC; 12 are specific to this condition. Other listed values are 30CrMnSiA reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
30CrMnSiA QT35-40HRC 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
30CrMnSiA QT35-40HRC has a yield strength of 1,080 MPa (157 ksi) and a tensile strength of 1,230 MPa (178 ksi) — stronger than 93% of steel grades. Elongation at break is 11% and the elastic modulus is 210 GPa (30.5 Msi).
Thermal6
30CrMnSiA QT35-40HRC is rated for continuous service to 350°C (662 °F). It conducts heat at 38 W/m·K (22 BTU/hr·ft·°F), worse than 69% of steel grades. Thermal expansion is 11.3 µm/m·K (6.28 µin/in·°F).
Electrical3
30CrMnSiA QT35-40HRC conducts electricity at 7.2 % IACS, worse than 71% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of 30CrMnSiA QT35-40HRC takes about 34 MJ of energy and emits 2.4 kg of CO₂ — more than 82% of steel grades. Typical recycled content is 25%.
Manufacturability7
30CrMnSiA QT35-40HRC's machinability is fair (36/100, worse than 81% of steel grades); weldability good (55/100); formability fair (35/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 30CrMnSiA QT35-40HRC
Is 30CrMnSiA easy to machine?
Machine in the annealed/normalized state (≈45–60 % of AISI 1212); above 35 HRC use carbide or CBN with rigid setups and reduced feed; leave grinding stock for post-Q&T distortion.
Can 30CrMnSiA be welded?
Good TIG/MIG/resistance weldability up to ~4 mm; preheat 150–300 °C for thick sections, use ER80S-D2/matching filler, and temper or fully re-Q&T after welding to avoid martensitic HAZ cracking.
Can 30CrMnSiA be formed, bent or molded?
Cold bend and roll only in the annealed condition (min bend radius ≈2t); hot forge at 1150–850 °C then normalize; oil quench from 860–890 °C, temper 200–600 °C to the required strength level.
What surface finishes work on 30CrMnSiA?
No corrosion resistance bare — apply Cd or Zn plating, phosphate + primer, or hard chrome; bake at 190 °C for 8–23 h after plating above 1000 MPa to relieve hydrogen embrittlement; shot peening markedly improves fatigue life.
30CrMnSiA 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 | 0.28 – 0.34 | 0.31 |
| Si | 0.9 – 1.2 | 1.05 |
| Mn | 0.8 – 1.1 | 0.95 |
| Cr | 0.8 – 1.1 | 0.95 |
| Niresidual | ≤ 0.3 | 0.1 |
| Curesidual | ≤ 0.25 | 0.1 |
| Moresidual, not intentionally added | ≤ 0.1 | — |
| P'A' high-grade limit | ≤ 0.03 | 0.01 |
| S'A' high-grade limit | ≤ 0.03 | 0.01 |
| Fe | balance | — |
30CrMnSiA QT35-40HRC — frequently asked
What is 30CrMnSiA QT35-40HRC used for?
30CrMnSiA QT35-40HRC is typically used for aircraft parts, high-strength fasteners and landing gear components. In short: aerospace-quality 4130 equivalent; weldable up to 4 mm; tempers to 1470 MPa.
What is the yield strength of 30CrMnSiA QT35-40HRC?
30CrMnSiA QT35-40HRC has a typical yield strength of 1,080 MPa (157 ksi) and a tensile strength of 1,230 MPa (178 ksi) — stronger than 93% of steel grades. Strength varies by condition: see the 10 listed tempers.
Is 30CrMnSiA QT35-40HRC easy to machine?
Not especially — machinability is rated fair (36/100, worse than 81% of steel grades). Machine in the annealed/normalized state (≈45–60 % of AISI 1212); above 35 HRC use carbide or CBN with rigid setups and reduced feed; leave grinding stock for post-Q&T distortion.
Can 30CrMnSiA QT35-40HRC be welded?
Yes — weldability is rated good (55/100). Good TIG/MIG/resistance weldability up to ~4 mm; preheat 150–300 °C for thick sections, use ER80S-D2/matching filler, and temper or fully re-Q&T after welding to avoid martensitic HAZ cracking.
What surface finishes work on 30CrMnSiA QT35-40HRC?
No corrosion resistance bare — apply Cd or Zn plating, phosphate + primer, or hard chrome; bake at 190 °C for 8–23 h after plating above 1000 MPa to relieve hydrogen embrittlement; shot peening markedly improves fatigue life.
Can 30CrMnSiA QT35-40HRC be formed, bent or molded?
Cold bend and roll only in the annealed condition (min bend radius ≈2t); hot forge at 1150–850 °C then normalize; oil quench from 860–890 °C, temper 200–600 °C to the required strength level.
What is the maximum service temperature of 30CrMnSiA QT35-40HRC?
30CrMnSiA QT35-40HRC is rated for continuous use to about 350°C (662 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 30CrMnSiA-QT1080 and 30CrMnSiA-A?
QT1080 is the default condition — standard GB/T 3077 delivery condition — best balance of 1100 MPa strength and toughness for structural parts. A: softest condition — choose for deep machining, cold forming or tube bending before final heat treatment. Yield strength is 930 MPa in QT1080 versus 420 MPa in A.
Sources
- GOST 4543 (30ХГСА structural alloy steel) — Gosstandart (2016)
- ASM Handbook Vol.1: Properties and Selection — Irons, Steels, and High-Performance Alloys — ASM International (1990)
- MMPDS-17 (AISI 4130/4135 low-alloy steel chapters, used as analogue) — Battelle/FAA (2022)
- (30CrMnSiA) — Mysteel / 1688 (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.