Steel 27SiMn-QT (Quenched and tempered)
Heat-treated state · default condition
GB 27SiMn
The standard supply and design condition — full GB/T 3077 strength with ≥39 J toughness for cylinder tubes and drill collars.
Values for the QT condition
Other 27SiMn tempers and conditions
27SiMn is listed in 9 conditions; see the grade overview at 27SiMn.
Compare all 9 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Solution annealed | Softest condition — pick for deep machining, cold sizing or before final quench and temper. | 350 | 620 | 22 | 200 HB | — |
Hot rolled | Cheapest mill condition for stock that will be heat treated after machining or forging. | 420 | 750 | 18 | 225 HB | — |
Normalized | Uniform fine-pearlite structure — used to refine forging grain and stabilise machining stock. | 470 | 800 | 17 | 22 HRC | 7 % IACS |
Normalized and tempered | Choose for large sections where water quenching risks cracking but medium strength is enough. | 480 | 760 | 19 | 20 HRC | 7 % IACS |
Cold drawn | Tight tolerance tube/bar with work-hardened strength — the usual precursor for honed hydraulic cylinder tube. | 700 | 900 | 12 | 26 HRC | 6.8 % IACS |
Q&T to 28–32 HRC | Pick when impact toughness and machinability matter more than peak strength (drill-collar bodies, thick cylinders). | 820 | 960 | 16 | 30 HRC | — |
QTDefaultThis page Quenched and tempered | The standard supply and design condition — full GB/T 3077 strength with ≥39 J toughness for cylinder tubes and drill collars. | 890 | 1,030 | 15 | 32 HRC | — |
Q&T core + induction hardened surface | For piston rods and journals needing 50+ HRC wear surface over a tough Q&T core; high Si aids hardenability. | 890 | 1,030 | 13 | 52 HRC | 6.6 % IACS |
Q&T to 34–38 HRC | Use where wear and yield strength dominate — downhole tool joints, pins, wear sleeves; toughness drops. | 1,000 | 1,150 | 13 | 36 HRC | — |
What is 27SiMn-QT?
27SiMn-QT is 27SiMn heat treated to QT — the standard supply and design condition — full GB/T 3077 strength with ≥39 J toughness for cylinder tubes and drill collars. 27SiMn-QT has a yield strength of 890 MPa (129 ksi) and a tensile strength of 1,030 MPa (149 ksi) — stronger than 90% of steel grades. Elongation at break is 15% and the elastic modulus is 210 GPa (30.5 Msi). 27SiMn-QT 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).
Advantages
- High strength — 890 MPa (129 ksi), better than 90% of steel grades
- Polishes to a fine finish — 65/100, better than 78% of steel grades
Limitations
- Low electrical conductivity — 6.6 % IACS, worse than 76% of steel grades
27SiMn-QT properties
Typical room-temperature values for 27SiMn-QT; 15 are specific to this condition. Other listed values are 27SiMn reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
27SiMn-QT 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).
Mechanical15
27SiMn-QT has a yield strength of 890 MPa (129 ksi) and a tensile strength of 1,030 MPa (149 ksi) — stronger than 90% of steel grades. Elongation at break is 15% and the elastic modulus is 210 GPa (30.5 Msi).
Thermal6
27SiMn-QT 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 12.3 µm/m·K (6.83 µin/in·°F).
Electrical3
27SiMn-QT conducts electricity at 6.6 % IACS, worse than 76% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (11/100), worse than 73% of steel grades.
Sustainability4
Producing a kilogram of 27SiMn-QT takes about 26 MJ of energy and emits 2 kg of CO₂ — less than 64% of steel grades. Typical recycled content is 25%.
Manufacturability7
27SiMn-QT's machinability is fair (45/100, worse than 65% of steel grades); weldability fair (35/100); formability poor (25/100).
Common Calculations5
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 27SiMn-QT
Is 27SiMn easy to machine?
Machine in the annealed or normalized condition (≤217 HB) with carbide tooling; at 30+ HRC after Q&T expect ~50 % of 1212 speeds and abrasive tool wear from the high silicon.
Can 27SiMn be welded?
CE ≈0.6–0.7 — preheat 200–300 °C, use low-hydrogen consumables and temper/stress-relieve at 550–600 °C after welding; avoid welding in the fully hardened state.
Can 27SiMn be formed, bent or molded?
Hot forge 1150–850 °C then normalize; cold forming only in the annealed condition, cold-drawn tube must be stress-relieved before heavy bending.
What surface finishes work on 27SiMn?
No anodizing (ferrous); protect with phosphating plus oil, zinc plating, paint, or hard chrome plating on piston rods; bores are typically skive-roller-burnished or honed to Ra ≤0.4 µm.
27SiMn 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 | 0.24 – 0.32 | 0.28 |
| Si | 1.1 – 1.4 | 1.25 |
| Mn | 1.1 – 1.4 | 1.25 |
| Crresidual | ≤ 0.3 | — |
| Niresidual | ≤ 0.3 | — |
| Curesidual | ≤ 0.25 | — |
| P | ≤ 0.04 | — |
| S | ≤ 0.04 | — |
| Fe | balance | — |
27SiMn-QT — frequently asked
What is 27SiMn-QT used for?
27SiMn-QT is typically used for drill pipe, downhole tools and fasteners. In short: chromium-free drill-pipe steel; honed-tube alloy grade; lower-cost 4140 substitute.
What is the yield strength of 27SiMn-QT?
27SiMn-QT has a typical yield strength of 890 MPa (129 ksi) and a tensile strength of 1,030 MPa (149 ksi) — stronger than 90% of steel grades. Strength varies by condition: see the 9 listed tempers.
Is 27SiMn-QT easy to machine?
Reasonably — machinability is rated fair (45/100, worse than 65% of steel grades). Machine in the annealed or normalized condition (≤217 HB) with carbide tooling; at 30+ HRC after Q&T expect ~50 % of 1212 speeds and abrasive tool wear from the high silicon.
Can 27SiMn-QT be welded?
With care — weldability is rated fair (35/100). CE ≈0.6–0.7 — preheat 200–300 °C, use low-hydrogen consumables and temper/stress-relieve at 550–600 °C after welding; avoid welding in the fully hardened state.
What surface finishes work on 27SiMn-QT?
No anodizing (ferrous); protect with phosphating plus oil, zinc plating, paint, or hard chrome plating on piston rods; bores are typically skive-roller-burnished or honed to Ra ≤0.4 µm.
Can 27SiMn-QT be formed, bent or molded?
Hot forge 1150–850 °C then normalize; cold forming only in the annealed condition, cold-drawn tube must be stress-relieved before heavy bending.
What is the maximum service temperature of 27SiMn-QT?
27SiMn-QT 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 27SiMn-QT and 27SiMn-A?
QT is the default condition — the standard supply and design condition — full GB/T 3077 strength with ≥39 J toughness for cylinder tubes and drill collars. A: softest condition — pick for deep machining, cold sizing or before final quench and temper. Yield strength is 890 MPa in QT versus 350 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.