Steel 27Q120-SRA
Heat-treated state
EN 27Q120
SRA = stress-relief annealed after cutting/winding
Use for wound cores and precision laminations where the cutting/bending stress must be removed to recover the guaranteed core loss.
Values for the SRA condition
What is 27Q120-SRA?
27Q120-SRA is 27Q120 heat treated to SRA — use for wound cores and precision laminations where the cutting/bending stress must be removed to recover the guaranteed core loss. 27Q120-SRA has a yield strength of 300 MPa (43.5 ksi) and a tensile strength of 340 MPa (49.3 ksi) — weaker than 86% of steel grades. Elongation at break is 15% and the elastic modulus is 115 GPa (16.7 Msi). 27Q120-SRA has a density of 7.65 g/cm³ (0.276 lb/in³), lighter than 97% of steel grades. It melts at 1,470°C (2,678 °F).
Advantages
- Good corrosion resistance — 25/100, better than 92% of steel grades
Limitations
- Low stiffness — 115 GPa (16.7 Msi), worse than 100% of steel grades
- Hard to polish — 30/100, worse than 100% of steel grades
- Limited service temperature — 150°C (302 °F), worse than 99% of steel grades
- Poor heat conductor — 22 W/m·K (12.7 BTU/hr·ft·°F), worse than 93% of steel grades
- High embodied carbon — 2.6 kg CO₂/kg, worse than 87% of steel grades
27Q120-SRA properties
Typical room-temperature values for 27Q120-SRA; 6 are specific to this condition. Other listed values are 27Q120 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
27Q120-SRA has a density of 7.65 g/cm³ (0.276 lb/in³), lighter than 97% of steel grades. It melts at 1,470°C (2,678 °F).
Mechanical12
27Q120-SRA has a yield strength of 300 MPa (43.5 ksi) and a tensile strength of 340 MPa (49.3 ksi) — weaker than 86% of steel grades. Elongation at break is 15% and the elastic modulus is 115 GPa (16.7 Msi).
Thermal6
27Q120-SRA is rated for continuous service to 150°C (302 °F). It conducts heat at 22 W/m·K (12.7 BTU/hr·ft·°F), worse than 93% of steel grades. Thermal expansion is 11.6 µm/m·K (6.44 µin/in·°F).
Electrical3
27Q120-SRA conducts electricity at 3.6 % IACS, worse than 85% of steel grades.
Chemical & Environmental2
Corrosion resistance is poor (25/100), better than 92% of steel grades.
Sustainability4
Producing a kilogram of 27Q120-SRA takes about 34 MJ of energy and emits 2.6 kg of CO₂ — more than 82% of steel grades. Typical recycled content is 15%.
Manufacturability7
27Q120-SRA's machinability is fair (35/100, worse than 84% of steel grades); weldability poor (30/100); formability fair (35/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 27Q120-SRA
Is 27Q120 easy to machine?
Not machined conventionally — blank by precision shearing, guillotine or carbide/PCD punching with tight clearance and sharp tools; burr height should stay under ~20 µm to avoid interlaminar shorts.
Can 27Q120 be welded?
Avoid welding in the magnetic path; any TIG/laser tack destroys the Goss texture and coating locally — use clamping, banding or edge tack welds outside the flux path.
Can 27Q120 be formed, bent or molded?
3 % Si makes the strip brittle: only slitting, shearing, mitre cutting and large-radius winding are practical; no deep drawing or tight bending.
What surface finishes work on 27Q120?
Supplied ready-coated with a C-5 type phosphate insulating film; if cutting or annealing damages it, re-coat or varnish edges, and stress-relief anneal at ~800 °C in dry N₂/H₂ before re-coating.
27Q120 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 |
|---|---|---|
| Sigives ~48 µΩ·cm resistivity, lowers eddy-current loss | 2.9 – 3.3 | 3.1 |
| Cafter decarburizing anneal; ≤0.003 % in final product | ≤ 0.01 | 0 |
| Mn | 0.03 – 0.2 | 0.1 |
| SMnS used as inhibitor, largely removed in high-temperature anneal | ≤ 0.01 | 0.01 |
| P | ≤ 0.03 | 0.02 |
| AlAlN inhibitor route | ≤ 0.04 | 0.02 |
| N | ≤ 0.01 | 0 |
| Cuinhibitor addition in some mill routes | ≤ 0.6 | 0.1 |
| Fe | balance |
27Q120-SRA — frequently asked
What is 27Q120-SRA used for?
27Q120-SRA is typically used for power transformer cores, instrument transformer cores, distribution transformer laminations, step-lap stacked core assemblies, wound toroidal cores and slit strip for core winding. In short: lower loss than 30Q140; thin 0.27 mm grain-oriented; shear and wind only.
What is the yield strength of 27Q120-SRA?
27Q120-SRA has a typical yield strength of 300 MPa (43.5 ksi) and a tensile strength of 340 MPa (49.3 ksi) — weaker than 86% of steel grades.
Is 27Q120-SRA easy to machine?
Not especially — machinability is rated fair (35/100, worse than 84% of steel grades). Not machined conventionally — blank by precision shearing, guillotine or carbide/PCD punching with tight clearance and sharp tools; burr height should stay under ~20 µm to avoid interlaminar shorts.
Can 27Q120-SRA be welded?
Not readily — weldability is rated poor (30/100). Avoid welding in the magnetic path; any TIG/laser tack destroys the Goss texture and coating locally — use clamping, banding or edge tack welds outside the flux path.
What surface finishes work on 27Q120-SRA?
Supplied ready-coated with a C-5 type phosphate insulating film; if cutting or annealing damages it, re-coat or varnish edges, and stress-relief anneal at ~800 °C in dry N₂/H₂ before re-coating.
Can 27Q120-SRA be formed, bent or molded?
3 % Si makes the strip brittle: only slitting, shearing, mitre cutting and large-radius winding are practical; no deep drawing or tight bending.
What is the maximum service temperature of 27Q120-SRA?
27Q120-SRA is rated for continuous use to about 150°C (302 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
Sources
- IEC 60404-8-7 Magnetic materials — Specifications for grain-oriented steel sheet and strip — IEC (2020)
- Grain-oriented electrical steel product catalogue — Baosteel / (2023)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels and High-Performance Alloys (magnetically soft materials) — 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.