Steel 30CrMnSiNi2A IsoQ
Heat-treated state
EN 30CrMnSiNi2A
IsoQ = isothermal quench (austemper, lower bainite)
Choose for complex thin-section forgings where distortion and quench cracking must be minimised and impact toughness maximised.
Values for the IsoQ condition
Other 30CrMnSiNi2A tempers and conditions
30CrMnSiNi2A is listed in 10 conditions; see the grade overview at 30CrMnSiNi2A.
Compare all 10 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
(mill delivery condition for bar/forging stock) | Soft delivery condition for machining, cold straightening and forging stock before final quench and temper. | 560 | 800 | 18 | 217 HB | — |
Cold drawn + annealed bar | Small-diameter precision bar for fasteners and pins, machined then heat treated to final strength. | 720 | 900 | 12 | 25 HRC | 6.4 % IACS |
Normalized + high-temperature temper | Alternative pre-machining condition giving a uniform sorbitic structure and better machined surface than full anneal. | 750 | 950 | 16 | 27 HRC | 6.4 % IACS |
Q&T 500–550 °C | Use when maximum toughness, machinability and reduced SCC/hydrogen sensitivity matter more than peak strength. | 1,150 | 1,280 | 15 | 39 HRC | — |
IsoQThis page Isothermal quench (austemper, lower bainite) | Choose for complex thin-section forgings where distortion and quench cracking must be minimised and impact toughness maximised. | 1,300 | 1,550 | 14 | 45 HRC | — |
Q&T 400 °C | Listed for reference only — tempering near 350–450 °C causes a sharp drop in impact energy and should be avoided. | 1,350 | 1,500 | 12 | 44 HRC | 5.9 % IACS |
Q&T 300 °C | Slightly lower strength with improved toughness and hot-strength retention; upper limit before temper embrittlement. | 1,400 | 1,630 | 13 | 46 HRC | — |
QT260Default Q&T 260 °C | Standard aerospace condition — best balance of 1620–1800 MPa strength, ductility and K_IC for landing gear and structural fittings. | 1,450 | 1,700 | 12 | 48 HRC | — |
As-quenched (untempered martensite) | Intermediate condition only — never used in service because untempered martensite is brittle and quench-crack prone. | 1,550 | 2,000 | 5 | 54 HRC | 4.5 % IACS |
Q&T 200 °C | Maximum-strength condition for short-life or stiffness-critical parts where toughness and SCC resistance are less critical. | 1,550 | 1,820 | 10 | 51 HRC | — |
What is 30CrMnSiNi2A IsoQ?
30CrMnSiNi2A IsoQ is 30CrMnSiNi2A heat treated to IsoQ — choose for complex thin-section forgings where distortion and quench cracking must be minimised and impact toughness maximised. 30CrMnSiNi2A IsoQ has a yield strength of 1,300 MPa (189 ksi) and a tensile strength of 1,550 MPa (225 ksi) — stronger than 95% of steel grades. Elongation at break is 14% and the elastic modulus is 200 GPa (29 Msi). 30CrMnSiNi2A IsoQ has a density of 7.8 g/cm³ (0.282 lb/in³), lighter than 87% of steel grades. It melts at 1,420°C (2,588 °F). QT260 is the default condition FabDigit quotes; IsoQ is available on request or by drawing note.
Advantages
- High strength — 1,300 MPa (189 ksi), better than 95% of steel grades
- Polishes to a fine finish — 70/100, better than 87% of steel grades
Limitations
- Limited formability — 10/100, worse than 95% of steel grades
- Difficult to machine — 25/100, worse than 93% of steel grades
- Difficult to weld — 20/100, worse than 84% of steel grades
- Poor heat conductor — 31 W/m·K (17.9 BTU/hr·ft·°F), worse than 83% of steel grades
- Limited service temperature — 280°C (536 °F), worse than 82% of steel grades
30CrMnSiNi2A IsoQ properties
Typical room-temperature values for 30CrMnSiNi2A IsoQ; 10 are specific to this condition. Other listed values are 30CrMnSiNi2A reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
30CrMnSiNi2A IsoQ has a density of 7.8 g/cm³ (0.282 lb/in³), lighter than 87% of steel grades. It melts at 1,420°C (2,588 °F).
Mechanical15
30CrMnSiNi2A IsoQ has a yield strength of 1,300 MPa (189 ksi) and a tensile strength of 1,550 MPa (225 ksi) — stronger than 95% of steel grades. Elongation at break is 14% and the elastic modulus is 200 GPa (29 Msi).
Thermal6
30CrMnSiNi2A IsoQ is rated for continuous service to 280°C (536 °F). It conducts heat at 31 W/m·K (17.9 BTU/hr·ft·°F), worse than 83% of steel grades. Thermal expansion is 11.5 µm/m·K (6.39 µin/in·°F).
Electrical3
30CrMnSiNi2A IsoQ conducts electricity at 5.7 % IACS, worse than 80% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of 30CrMnSiNi2A IsoQ takes about 34 MJ of energy and emits 2.5 kg of CO₂ — more than 82% of steel grades. Typical recycled content is 20%.
Manufacturability7
30CrMnSiNi2A IsoQ's machinability is poor (25/100, worse than 93% of steel grades); weldability poor (20/100); formability not recommended (10/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 30CrMnSiNi2A IsoQ
Is 30CrMnSiNi2A easy to machine?
Rough-machine in the annealed condition (HB ≤229); finish cuts on hardened 48 HRC material need rigid setups, coated carbide or CBN, low feeds and generous coolant, leaving stock for grinding.
Can 30CrMnSiNi2A be welded?
Poor weldability — if unavoidable use TIG/EB with matching or low-hydrogen filler, 250–350 °C preheat, and re-quench-and-temper the whole part; never weld in the final heat-treated state.
Can 30CrMnSiNi2A be formed, bent or molded?
Hot forge 1150→900 °C with slow post-forge cooling and immediate anneal; cold forming is limited to gentle straightening in the annealed state.
What surface finishes work on 30CrMnSiNi2A?
Shot-peen highly stressed fillets, then cadmium, Zn-Ni or IVD aluminium plate plus primer; bake 190–200 °C for 8–24 h after plating or acid pickling to relieve hydrogen, and avoid grinding burns.
30CrMnSiNi2A 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 | 0.27 – 0.34 | 0.3 |
| Siraises tempering resistance | 0.9 – 1.2 | 1.05 |
| Mn | 1 – 1.3 | 1.15 |
| Cr | 0.9 – 1.2 | 1.05 |
| Nitoughness and hardenability | 1.4 – 1.8 | 1.6 |
| Curesidual | ≤ 0.2 | — |
| Saerospace melt practice, often ≤0.008 | ≤ 0.01 | — |
| P | ≤ 0.02 | — |
| Fe | balance | — |
30CrMnSiNi2A IsoQ — frequently asked
What is 30CrMnSiNi2A IsoQ used for?
30CrMnSiNi2A IsoQ is typically used for landing gear, aircraft structural forgings and high-strength shafts. In short: 300M-class strength level; silicon-modified temper resistance; landing gear workhorse grade.
What is the yield strength of 30CrMnSiNi2A IsoQ?
30CrMnSiNi2A IsoQ has a typical yield strength of 1,300 MPa (189 ksi) and a tensile strength of 1,550 MPa (225 ksi) — stronger than 95% of steel grades. Strength varies by condition: see the 10 listed tempers.
Is 30CrMnSiNi2A IsoQ easy to machine?
Not especially — machinability is rated poor (25/100, worse than 93% of steel grades). Rough-machine in the annealed condition (HB ≤229); finish cuts on hardened 48 HRC material need rigid setups, coated carbide or CBN, low feeds and generous coolant, leaving stock for grinding.
Can 30CrMnSiNi2A IsoQ be welded?
Not readily — weldability is rated poor (20/100). Poor weldability — if unavoidable use TIG/EB with matching or low-hydrogen filler, 250–350 °C preheat, and re-quench-and-temper the whole part; never weld in the final heat-treated state.
What surface finishes work on 30CrMnSiNi2A IsoQ?
Shot-peen highly stressed fillets, then cadmium, Zn-Ni or IVD aluminium plate plus primer; bake 190–200 °C for 8–24 h after plating or acid pickling to relieve hydrogen, and avoid grinding burns.
Can 30CrMnSiNi2A IsoQ be formed, bent or molded?
Hot forge 1150→900 °C with slow post-forge cooling and immediate anneal; cold forming is limited to gentle straightening in the annealed state.
What is the maximum service temperature of 30CrMnSiNi2A IsoQ?
30CrMnSiNi2A IsoQ is rated for continuous use to about 280°C (536 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 30CrMnSiNi2A-QT260 and 30CrMnSiNi2A-QT520?
QT260 is the default condition — standard aerospace condition — best balance of 1620–1800 MPa strength, ductility and K_IC for landing gear and structural fittings. QT520: use when maximum toughness, machinability and reduced SCC/hydrogen sensitivity matter more than peak strength. Yield strength is 1,450 MPa in QT260 versus 1,150 MPa in QT520.
Sources
- GJB / (30CrMnSiNi2A) (1994)
- ASM Handbook Vol.1: Properties and Selection — Irons, Steels, and High-Performance Alloys — ASM International (1990)
- MMPDS-17 (300M / AMS 6417 comparison data) — Battelle (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.