Steel M27-SRA
Heat-treated state
AISI/SAE M27
SRA = stress-relief annealed after punching
Use when punching/edge stresses have raised core loss; the anneal recovers magnetic performance at the cost of softening the laminations.
Values for the SRA condition
Other M27 tempers and conditions
M27 is listed in 3 conditions; see the grade overview at M27.
Compare all 3 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
SRAThis page Stress-relief annealed after punching | Use when punching/edge stresses have raised core loss; the anneal recovers magnetic performance at the cost of softening the laminations. | 280 | 420 | 33 | 147 HB | 3.8 % IACS |
Semi-processed, 0.64 mm | Heavy-gauge semi-processed coil for high-volume punched stators/rotors that are annealed in the assembly line. | 365 | 475 | 22 | 8 HRC | 3.8 % IACS |
Semi-processed, 0.47 mm | Choose when laminations are punched hard and then decarburize/grain-grow annealed by the customer to reach final magnetic quality. | 370 | 480 | 20 | 9 HRC | 3.8 % IACS |
What is M27-SRA?
M27-SRA is M27 heat treated to SRA — use when punching/edge stresses have raised core loss; the anneal recovers magnetic performance at the cost of softening the laminations. M27-SRA has a yield strength of 280 MPa (40.6 ksi) and a tensile strength of 420 MPa (60.9 ksi) — weaker than 90% of steel grades. Elongation at break is 33% and the elastic modulus is 200 GPa (29 Msi). M27-SRA has a density of 7.75 g/cm³ (0.28 lb/in³), lighter than 93% of steel grades. It melts at 1,500°C (2,732 °F).
Advantages
- Ductile — tolerates forming and impact — 33%, better than 96% of steel grades
- Forms and bends easily — 72/100, better than 88% of steel grades
Limitations
- Limited service temperature — 200°C (392 °F), worse than 93% of steel grades
- Low strength — 280 MPa (40.6 ksi), worse than 90% of steel grades
- Poor heat conductor — 26 W/m·K (15 BTU/hr·ft·°F), worse than 87% of steel grades
- Low electrical conductivity — 3.8 % IACS, worse than 84% of steel grades
- Hard to polish — 45/100, worse than 84% of steel grades
M27-SRA properties
Typical room-temperature values for M27-SRA; 21 are specific to this condition. Other listed values are M27 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
M27-SRA has a density of 7.75 g/cm³ (0.28 lb/in³), lighter than 93% of steel grades. It melts at 1,500°C (2,732 °F).
Mechanical11
M27-SRA has a yield strength of 280 MPa (40.6 ksi) and a tensile strength of 420 MPa (60.9 ksi) — weaker than 90% of steel grades. Elongation at break is 33% and the elastic modulus is 200 GPa (29 Msi).
Thermal6
M27-SRA is rated for continuous service to 200°C (392 °F). It conducts heat at 26 W/m·K (15 BTU/hr·ft·°F), worse than 87% of steel grades. Thermal expansion is 11.8 µm/m·K (6.56 µin/in·°F).
Electrical3
M27-SRA conducts electricity at 3.8 % IACS, worse than 84% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (14/100), better than 70% of steel grades.
Sustainability4
Producing a kilogram of M27-SRA takes about 34 MJ of energy and emits 2.5 kg of CO₂ — more than 82% of steel grades. Typical recycled content is 25%.
Manufacturability7
M27-SRA's machinability is fair (44/100, worse than 71% of steel grades); weldability good (58/100); formability very good (72/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with M27-SRA
Is M27 easy to machine?
Blank and punch rather than machine — the Si content is abrasive, so use carbide/PM tooling, tight die clearance (5–8 % of thickness) and frequent regrinds to control burrs that short laminations.
Can M27 be welded?
TIG/laser stack welding is possible but the weld and HAZ short the laminations and raise local loss; keep welds short, outside the flux path, or use interlock/bonding instead.
Can M27 be formed, bent or molded?
Excellent for flat blanking, interlocking and light bending; avoid deep drawing or tight bend radii (<2t) since silicon steel has limited ductility and notch sensitivity.
What surface finishes work on M27?
Normally used with the mill C-3/C-5 insulating coating; bare edges rust, so varnish-dip, resin-encapsulate or paint assembled cores — no anodizing applies.
M27 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 |
|---|---|---|
| Siprincipal resistivity-raising addition; Si+Al ≈ 2.3–2.8 % | 1.8 – 2.6 | 2.3 |
| Alpart of the Si+Al loss-control balance | 0.15 – 0.6 | 0.35 |
| Mn | 0.1 – 0.5 | 0.3 |
| Cdecarburized in fully processed product | ≤ 0.01 | 0 |
| Psometimes added for strength/resistivity | ≤ 0.05 | 0.02 |
| S | ≤ 0.01 | 0.01 |
| N | ≤ 0.01 | 0 |
| Febalance; ASTM A677 specifies magnetic properties rather than a strict chemistry | balance | — |
M27-SRA — frequently asked
What is M27-SRA used for?
M27-SRA is typically used for general-purpose motors, ballasts and small transformers. In short: low-cost non-oriented lamination; higher core loss than M19; isotropic magnetic properties.
What is the yield strength of M27-SRA?
M27-SRA has a typical yield strength of 280 MPa (40.6 ksi) and a tensile strength of 420 MPa (60.9 ksi) — weaker than 90% of steel grades. Strength varies by condition: see the 3 listed tempers.
Is M27-SRA easy to machine?
Not especially — machinability is rated fair (44/100, worse than 71% of steel grades). Blank and punch rather than machine — the Si content is abrasive, so use carbide/PM tooling, tight die clearance (5–8 % of thickness) and frequent regrinds to control burrs that short laminations.
Can M27-SRA be welded?
Yes — weldability is rated good (58/100). TIG/laser stack welding is possible but the weld and HAZ short the laminations and raise local loss; keep welds short, outside the flux path, or use interlock/bonding instead.
What surface finishes work on M27-SRA?
Normally used with the mill C-3/C-5 insulating coating; bare edges rust, so varnish-dip, resin-encapsulate or paint assembled cores — no anodizing applies.
Can M27-SRA be formed, bent or molded?
Excellent for flat blanking, interlocking and light bending; avoid deep drawing or tight bend radii (<2t) since silicon steel has limited ductility and notch sensitivity.
What is the maximum service temperature of M27-SRA?
M27-SRA is rated for continuous use to about 200°C (392 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
Sources
- ASTM A677 — Nonoriented Electrical Steel Fully Processed Types — ASTM International (2020)
- ASTM A683 — Nonoriented Electrical Steel Semiprocessed Types — ASTM International (2019)
- ASTM A976 — Classification of Insulating Coatings for Electrical Steels — ASTM International (2019)
- Non-Oriented Electrical Steels (M-15 … M-45) product data — Cleveland-Cliffs (formerly AK Steel) (2021)
- 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.