Steel M-3-SRA
Heat-treated state
SRA = stress-relief annealed after shearing/forming
Apply this ≈800–840 °C protective-atmosphere anneal to wound or punched and bent cores to recover core loss raised by processing stress; yield falls to 295 MPa, elongation rises to 12%.
Values for the SRA condition
Other M-3 tempers and conditions
M-3 is listed in 2 conditions; see the grade overview at M-3.
- SRA
- DR
Compare all 2 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
SRAThis page Stress-relief annealed after shearing/forming | Apply this ≈800–840 °C protective-atmosphere anneal to wound or punched and bent cores to recover core loss raised by processing stress; yield falls to 295 MPa, elongation rises to 12%. | 295 | 340 | 12 | 150 HB | 3.6 % IACS |
Domain refined (laser/mechanically scribed) Hi-B strip | Use laser- or mechanically scribed domain-refined Hi-B strip for large transformer stacked cores needing the lowest core loss with no stress-relief anneal; mechanical properties are unchanged. | 315 | 360 | 7 | 163 HB | 3.6 % IACS |
What is M-3-SRA?
M-3-SRA is M-3 heat treated to SRA — apply this ≈800–840 °C protective-atmosphere anneal to wound or punched and bent cores to recover core loss raised by processing stress; yield falls to 295 MPa, elongation rises to 12%. M-3-SRA has a yield strength of 295 MPa (42.8 ksi) and a tensile strength of 340 MPa (49.3 ksi) — weaker than 87% of steel grades. Elongation at break is 12% and the elastic modulus is 118 GPa (17.1 Msi). M-3-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).
Limitations
- Low stiffness — 118 GPa (17.1 Msi), worse than 99% of steel grades
- Poor heat conductor — 21 W/m·K (12.1 BTU/hr·ft·°F), worse than 95% of steel grades
- Limited service temperature — 200°C (392 °F), worse than 93% of steel grades
- Low strength — 295 MPa (42.8 ksi), worse than 87% of steel grades
- High embodied carbon — 2.6 kg CO₂/kg, worse than 87% of steel grades
M-3-SRA properties
Typical room-temperature values for M-3-SRA; 22 are specific to this condition. Other listed values are M-3 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
M-3-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).
Mechanical11
M-3-SRA has a yield strength of 295 MPa (42.8 ksi) and a tensile strength of 340 MPa (49.3 ksi) — weaker than 87% of steel grades. Elongation at break is 12% and the elastic modulus is 118 GPa (17.1 Msi).
Thermal6
M-3-SRA is rated for continuous service to 200°C (392 °F). It conducts heat at 21 W/m·K (12.1 BTU/hr·ft·°F), worse than 95% of steel grades. Thermal expansion is 11.5 µm/m·K (6.39 µin/in·°F).
Electrical3
M-3-SRA conducts electricity at 3.6 % IACS, worse than 85% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of M-3-SRA takes about 35 MJ of energy and emits 2.6 kg of CO₂ — more than 87% of steel grades. Typical recycled content is 15%.
Manufacturability6
M-3-SRA's machinability is fair (38/100, worse than 80% of steel grades); weldability fair (42/100); formability poor (32/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with M-3-SRA
Is M-3 easy to machine?
Work mainly by precision shearing, blanking and laser or waterjet cutting. The high silicon content wears dies quickly, so use carbide cutting edges and closely controlled die clearance to limit burrs and edge stress.
Can M-3 be welded?
Avoid welding between laminations — welds short the interlaminar insulation and raise core loss in the heat-affected zone. Where tacking is unavoidable, use low-heat-input TIG or laser spot welds followed by a stress-relief anneal.
Can M-3 be formed, bent or molded?
The material is hard, brittle and strongly anisotropic, so restrict work to shearing, slight bending or core winding. Anneal at 800–840 °C in a protective atmosphere after any cold work to restore magnetic properties.
What surface finishes work on M-3?
Supplied with a phosphate–magnesium silicate tension coating and needs no plating. For painting or bonding, remove the coating locally or use a compatible primer; varnish sheared edges for rust protection.
M-3 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 |
|---|---|---|
| Sicore alloying element; raises resistivity, lowers eddy-current loss | 2.9 – 3.4 | 3.15 |
| Cdecarburization annealed; very low C avoids magnetic aging | ≤ 0.01 | 0 |
| Mn | 0.03 – 0.2 | 0.1 |
| AlAlN inhibitor for the Hi-B process | 0.02 – 0.04 | 0.03 |
| Nforms AlN inhibitor with Al | ≤ 0.01 | 0.01 |
| SMnS inhibitor residue; low in finished product | ≤ 0.01 | 0.01 |
| P | ≤ 0.03 | 0.01 |
| Cuused as auxiliary inhibitor in some process routes | ≤ 0.3 | 0.1 |
| Fe | balance | — |
M-3-SRA — frequently asked
What is M-3-SRA used for?
M-3-SRA is typically used for large power transformer cores, high-efficiency distribution transformer cores, generator step-up transformer cores, mitre-cut stacked core laminations, wound C-cores and toroidal cores and shunt reactor cores. In short: lowest-loss grain-oriented grade; hi-B high-permeability steel; highest cost per kilogram.
What is the yield strength of M-3-SRA?
M-3-SRA has a typical yield strength of 295 MPa (42.8 ksi) and a tensile strength of 340 MPa (49.3 ksi) — weaker than 87% of steel grades. Strength varies by condition: see the 2 listed tempers.
Is M-3-SRA easy to machine?
Not especially — machinability is rated fair (38/100, worse than 80% of steel grades). Work mainly by precision shearing, blanking and laser or waterjet cutting. The high silicon content wears dies quickly, so use carbide cutting edges and closely controlled die clearance to limit burrs and edge stress.
Can M-3-SRA be welded?
With care — weldability is rated fair (42/100). Avoid welding between laminations — welds short the interlaminar insulation and raise core loss in the heat-affected zone. Where tacking is unavoidable, use low-heat-input TIG or laser spot welds followed by a stress-relief anneal.
What surface finishes work on M-3-SRA?
Supplied with a phosphate–magnesium silicate tension coating and needs no plating. For painting or bonding, remove the coating locally or use a compatible primer; varnish sheared edges for rust protection.
Can M-3-SRA be formed, bent or molded?
The material is hard, brittle and strongly anisotropic, so restrict work to shearing, slight bending or core winding. Anneal at 800–840 °C in a protective atmosphere after any cold work to restore magnetic properties.
What is the maximum service temperature of M-3-SRA?
M-3-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 A876/A876M — Flat-Rolled, Grain-Oriented, Silicon-Iron, Electrical Steel, Fully Processed Types — ASTM International (2020)
- ASTM A34/A34M — Practice for Sampling and Procurement Testing of Magnetic Materials — ASTM International (2021)
- Grain-Oriented Electrical Steels Product Data Bulletin — AK Steel / Cleveland-Cliffs (2019)
- 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.