Steel 30CrMnSi QT-ISO
Heat-treated state
GB 30CrMnSi
QT-ISO = isothermal (austempered) quench
Choose for thin high-strength parts where distortion and quench cracking must be minimised while keeping toughness at ~1600 MPa.
Values for the QT-ISO condition
Other 30CrMnSi tempers and conditions
30CrMnSi is listed in 8 conditions; see the grade overview at 30CrMnSi.
Compare all 8 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Solution annealed | Softest state — pick for deep machining, cold forming or thread rolling before final Q&T. | 480 | 750 | 20 | 210 HB | — |
Hot rolled | Cheapest mill condition for stock that will be fully heat treated after rough machining. | 520 | 850 | 15 | 240 HB | — |
Normalized | Uniform fine-grain structure for forgings before final quenching, or moderate-strength non-critical parts. | 620 | 950 | 14 | 29 HRC | — |
Cold drawn | Bright close-tolerance bar for shafts and fasteners machined without further heat treatment. | 750 | 900 | 10 | 27 HRC | 7 % IACS |
QT880-520Default Q&T | Standard commercial Q&T condition — best strength/toughness balance for shafts, gears, high-strength bolts and structural fittings. | 900 | 1,120 | 11 | 36 HRC | — |
Q&T | Higher-strength spring/fitting condition (~1300–1450 MPa) where some ductility is still needed. | 1,250 | 1,400 | 8 | 43 HRC | — |
QT-ISOThis page Isothermal (austempered) quench | Choose for thin high-strength parts where distortion and quench cracking must be minimised while keeping toughness at ~1600 MPa. | 1,350 | 1,600 | 8 | 46 HRC | — |
Q&T | Maximum-strength condition (1600–1700 MPa) for aircraft fittings and landing-gear parts; very notch- and hydrogen-sensitive. | 1,400 | 1,650 | 6 | 48 HRC | — |
What is 30CrMnSi QT-ISO?
30CrMnSi QT-ISO is 30CrMnSi heat treated to QT-ISO — choose for thin high-strength parts where distortion and quench cracking must be minimised while keeping toughness at ~1600 MPa. 30CrMnSi QT-ISO has a yield strength of 1,350 MPa (196 ksi) and a tensile strength of 1,600 MPa (232 ksi) — stronger than 95% of steel grades. Elongation at break is 8% and the elastic modulus is 205 GPa (29.7 Msi). 30CrMnSi QT-ISO 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). QT880-520 is the default condition FabDigit quotes; QT-ISO is available on request or by drawing note.
Advantages
- High strength — 1,350 MPa (196 ksi), better than 95% of steel grades
- Polishes to a fine finish — 65/100, better than 78% of steel grades
Limitations
- Limited ductility — 8%, worse than 95% of steel grades
- Difficult to machine — 25/100, worse than 93% of steel grades
- Low fracture toughness — 55 MPa·√m (50.1 ksi·√in), worse than 82% of steel grades
30CrMnSi QT-ISO properties
Typical room-temperature values for 30CrMnSi QT-ISO; 10 are specific to this condition. Other listed values are 30CrMnSi reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
30CrMnSi QT-ISO 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
30CrMnSi QT-ISO has a yield strength of 1,350 MPa (196 ksi) and a tensile strength of 1,600 MPa (232 ksi) — stronger than 95% of steel grades. Elongation at break is 8% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
30CrMnSi QT-ISO is rated for continuous service to 400°C (752 °F). It conducts heat at 37 W/m·K (21.4 BTU/hr·ft·°F), worse than 71% of steel grades. Thermal expansion is 11.5 µm/m·K (6.39 µin/in·°F).
Electrical3
30CrMnSi QT-ISO conducts electricity at 7 % IACS, worse than 74% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of 30CrMnSi QT-ISO 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
30CrMnSi QT-ISO's machinability is poor (25/100, worse than 93% of steel grades); weldability fair (40/100); formability poor (25/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 30CrMnSi QT-ISO
Is 30CrMnSi easy to machine?
Rough machine annealed or high-tempered (≤229 HB) with carbide at 100–150 m/min; above 40 HRC use coated carbide/CBN, rigid setups and finish-grind to size.
Can 30CrMnSi be welded?
Weldable but crack-prone: preheat 250–350 °C, low-hydrogen consumables or TIG with matching wire, slow cool and always temper/stress-relieve after welding; avoid welding parts already in the 1600 MPa condition.
Can 30CrMnSi be formed, bent or molded?
Cold form, bend and roll threads only in the annealed condition; hot forge 1150–1200 °C, finish above 900 °C, then slow cool or normalize to prevent flake cracking.
What surface finishes work on 30CrMnSi?
No anodizing — protect with zinc, cadmium or hard-chrome plating, phosphate + oil, black oxide or primer/paint; bake 190–200 °C for 4–24 h after plating high-strength tempers to relieve hydrogen embrittlement.
30CrMnSi 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 | — |
| Curesidual | ≤ 0.2 | — |
| Moresidual, not intentionally added | ≤ 0.1 | — |
| P≤0.025 for A-grade (30CrMnSiA) | ≤ 0.03 | — |
| S≤0.025 for A-grade (30CrMnSiA) | ≤ 0.03 | — |
| Fe | balance | — |
30CrMnSi QT-ISO — frequently asked
What is 30CrMnSi QT-ISO used for?
30CrMnSi QT-ISO is typically used for aircraft structural parts, high-strength bolts, shafts and landing gear. In short: high-strength Cr-Mn-Si structural steel; reaches 1600 MPa tempers; crack-sensitive when welded.
What is the yield strength of 30CrMnSi QT-ISO?
30CrMnSi QT-ISO has a typical yield strength of 1,350 MPa (196 ksi) and a tensile strength of 1,600 MPa (232 ksi) — stronger than 95% of steel grades. Strength varies by condition: see the 8 listed tempers.
Is 30CrMnSi QT-ISO easy to machine?
Not especially — machinability is rated poor (25/100, worse than 93% of steel grades). Rough machine annealed or high-tempered (≤229 HB) with carbide at 100–150 m/min; above 40 HRC use coated carbide/CBN, rigid setups and finish-grind to size.
Can 30CrMnSi QT-ISO be welded?
With care — weldability is rated fair (40/100). Weldable but crack-prone: preheat 250–350 °C, low-hydrogen consumables or TIG with matching wire, slow cool and always temper/stress-relieve after welding; avoid welding parts already in the 1600 MPa condition.
What surface finishes work on 30CrMnSi QT-ISO?
No anodizing — protect with zinc, cadmium or hard-chrome plating, phosphate + oil, black oxide or primer/paint; bake 190–200 °C for 4–24 h after plating high-strength tempers to relieve hydrogen embrittlement.
Can 30CrMnSi QT-ISO be formed, bent or molded?
Cold form, bend and roll threads only in the annealed condition; hot forge 1150–1200 °C, finish above 900 °C, then slow cool or normalize to prevent flake cracking.
What is the maximum service temperature of 30CrMnSi QT-ISO?
30CrMnSi QT-ISO 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 30CrMnSi QT880-520 and 30CrMnSi QT-ISO?
QT880-520 is the default condition — standard commercial Q&T condition — best strength/toughness balance for shafts, gears, high-strength bolts and structural fittings. QT-ISO: choose for thin high-strength parts where distortion and quench cracking must be minimised while keeping toughness at ~1600 MPa. Yield strength is 900 MPa in QT880-520 versus 1,350 MPa in QT-ISO.
Sources
- GOST 4543 Прокат из легированной конструкционной стали (30ХГСА) — Gosstandart (2016)
- 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.