Steel M-6-SRA
Heat-treated state
UNS T11306
SRA = laminations stress-relief annealed after shearing/punching
Pick when blanks are punched, bent or tightly wound: the anneal recovers the core loss and permeability lost to cutting strain, at the cost of slightly lower strength.
Values for the SRA condition
Other M-6 tempers and conditions
M-6 is listed in 4 conditions; see the grade overview at M-6.
Compare all 4 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
SRAThis page Laminations stress-relief annealed after shearing/punching | Pick when blanks are punched, bent or tightly wound: the anneal recovers the core loss and permeability lost to cutting strain, at the cost of slightly lower strength. | 295 | 335 | 12 | 160 HB | 3.6 % IACS |
Domain-refined (laser/mechanically scribed) 0.35 mm grain-oriented strip | Choose for lowest core loss in wound or stacked cores that will NOT be stress-relief annealed — the anneal erases the scribing benefit. | 315 | 350 | 7 | 172 HB | 3.6 % IACS |
Annealed | Soft supply condition of the cobalt-moly high-speed steel alias (0.8 C-4 W-5 Mo-4 Cr-1.5 V-12 Co) for machining tool blanks before hardening; not an electrical-steel condition. | 560 | 850 | 12 | 240 HB | 21 W/m·K |
Hardened & triple tempered | Service condition of the M6 HSS alias — austenitize ~1190-1210 °C, quench, temper 3× at 550-560 °C; chosen when 12 % Co red-hardness is needed for heavy-duty cutting. | — | 2,100 | 0.5 | 65 HRC | 24 W/m·K |
What is M-6-SRA?
M-6-SRA is M-6 heat treated to SRA — pick when blanks are punched, bent or tightly wound: the anneal recovers the core loss and permeability lost to cutting strain, at the cost of slightly lower strength. M-6-SRA has a yield strength of 295 MPa (42.8 ksi) and a tensile strength of 335 MPa (48.6 ksi) — weaker than 87% of steel grades. Elongation at break is 12% and the elastic modulus is 118 GPa (17.1 Msi). M-6-SRA has a density of 7.65 g/cm³ (0.276 lb/in³), lighter than 97% of steel grades. It melts at 1,480°C (2,696 °F).
Limitations
- Low stiffness — 118 GPa (17.1 Msi), worse than 99% of steel grades
- Limited service temperature — 200°C (392 °F), worse than 93% of steel grades
- Poor heat conductor — 23 W/m·K (13.3 BTU/hr·ft·°F), worse than 92% of steel grades
- Low strength — 295 MPa (42.8 ksi), worse than 87% of steel grades
- Low electrical conductivity — 3.6 % IACS, worse than 85% of steel grades
M-6-SRA properties
Typical room-temperature values for M-6-SRA; 21 are specific to this condition. Other listed values are M-6 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
M-6-SRA has a density of 7.65 g/cm³ (0.276 lb/in³), lighter than 97% of steel grades. It melts at 1,480°C (2,696 °F).
Mechanical11
M-6-SRA has a yield strength of 295 MPa (42.8 ksi) and a tensile strength of 335 MPa (48.6 ksi) — weaker than 87% of steel grades. Elongation at break is 12% and the elastic modulus is 118 GPa (17.1 Msi).
Thermal6
M-6-SRA is rated for continuous service to 200°C (392 °F). It conducts heat at 23 W/m·K (13.3 BTU/hr·ft·°F), worse than 92% of steel grades. Thermal expansion is 11.6 µm/m·K (6.44 µin/in·°F).
Electrical3
M-6-SRA conducts electricity at 3.6 % IACS, worse than 85% of steel grades.
Chemical & Environmental3
Corrosion resistance is poor (15/100), better than 75% of steel grades.
Sustainability4
Producing a kilogram of M-6-SRA takes about 34 MJ of energy and emits 2.4 kg of CO₂ — more than 82% of steel grades. Typical recycled content is 20%.
Manufacturability6
M-6-SRA's machinability is fair (38/100, worse than 80% of steel grades); weldability fair (40/100); formability fair (40/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with M-6-SRA
Is M-6 easy to machine?
Best processed by precision slitting, punching and laser/EDM cutting with carbide or coated tooling — the ceramic-like C-5 coating is abrasive and thermal cut edges must be de-burred; the M6 HSS variant is machined only in the annealed state and ground after hardening.
Can M-6 be welded?
TIG/laser tacking of core clamps is possible but any weld or heat-affected zone locally destroys the Goss texture and short-circuits laminations, so joints are kept off the flux path.
Can M-6 be formed, bent or molded?
Handle as a springy, notch-sensitive strip: shear along the rolling direction, keep bend radii generous, and stress-relief anneal at ~800 °C in inert atmosphere when strain is significant.
What surface finishes work on M-6?
Supplied with an inorganic phosphate/forsterite (C-5) insulating coating that also gives light rust protection; do not anodize (ferrous), and re-coat or oil any bare sheared edges.
M-6 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 |
|---|---|---|
| Siraises resistivity, lowers eddy-current loss | 2.9 – 3.3 | 3.1 |
| Cafter decarburization anneal; higher in as-rolled strip | ≤ 0.01 | 0 |
| Mnwith S forms MnS grain-growth inhibitor | 0.03 – 0.2 | 0.08 |
| S | ≤ 0.01 | 0 |
| AlAlN inhibitor route | ≤ 0.03 | 0.02 |
| N | ≤ 0.01 | 0.01 |
| P | ≤ 0.02 | 0.01 |
| Cuprocess-dependent inhibitor addition | ≤ 0.3 | 0.1 |
| Fe | balance | — |
M-6-SRA — frequently asked
What is M-6-SRA used for?
M-6-SRA is typically used for distribution transformer cores, power transformer cores, wound C-cores and toroidal cores, reactor and choke cores, current transformer cores and instrument transformer laminations. In short: standard grain-oriented transformer steel; lowest loss along rolling direction; lower cost than Hi-B.
What is the yield strength of M-6-SRA?
M-6-SRA has a typical yield strength of 295 MPa (42.8 ksi) and a tensile strength of 335 MPa (48.6 ksi) — weaker than 87% of steel grades. Strength varies by condition: see the 4 listed tempers.
Is M-6-SRA easy to machine?
Not especially — machinability is rated fair (38/100, worse than 80% of steel grades). Best processed by precision slitting, punching and laser/EDM cutting with carbide or coated tooling — the ceramic-like C-5 coating is abrasive and thermal cut edges must be de-burred; the M6 HSS variant is machined only in the annealed state and ground after hardening.
Can M-6-SRA be welded?
With care — weldability is rated fair (40/100). TIG/laser tacking of core clamps is possible but any weld or heat-affected zone locally destroys the Goss texture and short-circuits laminations, so joints are kept off the flux path.
What surface finishes work on M-6-SRA?
Supplied with an inorganic phosphate/forsterite (C-5) insulating coating that also gives light rust protection; do not anodize (ferrous), and re-coat or oil any bare sheared edges.
Can M-6-SRA be formed, bent or molded?
Handle as a springy, notch-sensitive strip: shear along the rolling direction, keep bend radii generous, and stress-relief anneal at ~800 °C in inert atmosphere when strain is significant.
What is the maximum service temperature of M-6-SRA?
M-6-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 — Flat-Rolled, Grain-Oriented, Silicon-Iron, Electrical Steel, Fully Processed Types — ASTM International (2018)
- ASTM A677 / A343 / A34 (electrical steel test and designation practice) — ASTM International (2020)
- Grain-oriented electrical steel product data (M-4/M-5/M-6 types) — Cleveland-Cliffs (former AK Steel) (2021)
- ASM Handbook Vol. 1: Properties and Selection — Irons, Steels, and High-Performance Alloys (magnetically soft materials; high-speed tool steels) — ASM International (1990)
- ASTM A600 — Tool Steel High Speed (AISI M6, UNS T11306) — ASTM International (2016)
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.