Steel M140-30P-SRA
Heat-treated state
SRA = stress-relief annealed after cutting
Choose for wound cores and heavily sheared laminations where cutting stresses must be removed to recover the guaranteed loss.
Values for the SRA condition
What is M140-30P-SRA?
M140-30P-SRA is M140-30P heat treated to SRA — choose for wound cores and heavily sheared laminations where cutting stresses must be removed to recover the guaranteed loss. M140-30P-SRA has a yield strength of 295 MPa (42.8 ksi) and a tensile strength of 320 MPa (46.4 ksi) — weaker than 87% of steel grades. Elongation at break is 13% and the elastic modulus is 120 GPa (17.4 Msi). M140-30P-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).
Advantages
- Good corrosion resistance — 22/100, better than 90% of steel grades
Limitations
- Low stiffness — 120 GPa (17.4 Msi), worse than 99% of steel grades
- Limited service temperature — 150°C (302 °F), worse than 99% of steel grades
- Hard to polish — 35/100, 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
- Difficult to machine — 30/100, worse than 89% of steel grades
M140-30P-SRA properties
Typical room-temperature values for M140-30P-SRA; 5 are specific to this condition. Other listed values are M140-30P reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
M140-30P-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
M140-30P-SRA has a yield strength of 295 MPa (42.8 ksi) and a tensile strength of 320 MPa (46.4 ksi) — weaker than 87% of steel grades. Elongation at break is 13% and the elastic modulus is 120 GPa (17.4 Msi).
Thermal6
M140-30P-SRA is rated for continuous service to 150°C (302 °F). It conducts heat at 21 W/m·K (12.1 BTU/hr·ft·°F), worse than 95% of steel grades. Thermal expansion is 11.8 µm/m·K (6.56 µin/in·°F).
Electrical3
M140-30P-SRA conducts electricity at 3.6 % IACS, worse than 85% of steel grades.
Chemical & Environmental3
Corrosion resistance is poor (22/100), better than 90% of steel grades.
Sustainability4
Producing a kilogram of M140-30P-SRA takes about 36 MJ of energy and emits 2.6 kg of CO₂ — more than 89% of steel grades. Typical recycled content is 20%.
Manufacturability7
M140-30P-SRA's machinability is poor (30/100, worse than 89% of steel grades); weldability poor (30/100); formability poor (32/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with M140-30P-SRA
Is M140-30P easy to machine?
Normally only slit, sheared, punched or laser/EDM cut to lamination shape — the Fe-3Si and its glass film are highly abrasive, so carbide tooling with tight clearance and frequent regrinding is required to limit burrs.
Can M140-30P be welded?
Avoid welding through the stack; TIG/laser tack welds break the interlaminar insulation and locally destroy the Goss texture, raising core loss — use clamping, banding or bonding instead.
Can M140-30P be formed, bent or molded?
Strip is brittle and strongly anisotropic; keep bends and core-winding radii generous, cut with the rolling direction along the flux path, and stress-relief anneal at ~800 °C in a protective atmosphere after forming.
What surface finishes work on M140-30P?
Supplied ready-coated (C-5 phosphate/forsterite or C-6 composite); do not pickle, blast or paint over it — protect cut edges against rust and handle to avoid scratching the insulating film.
M140-30P 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 |
|---|---|---|
| Sitypical producer chemistry; EN 10107 specifies magnetic properties, not composition | 2.9 – 3.3 | 3.1 |
| Cafter decarburization annealing | ≤ 0.01 | 0 |
| Mn | 0.05 – 0.25 | 0.12 |
| SMnS/AlN inhibitors controlled in processing | ≤ 0.01 | 0 |
| Alacid-soluble Al for AlN inhibitor (HGO route) | ≤ 0.04 | 0.02 |
| N | ≤ 0.01 | 0 |
| P | ≤ 0.03 | 0.01 |
| Cuused by some producers as inhibitor-forming element | ≤ 0.6 | 0.1 |
| Fe | balance |
M140-30P-SRA — frequently asked
What is M140-30P-SRA used for?
M140-30P-SRA is typically used for distribution transformer cores, power transformer cores, wound (unicore) transformer cores, reactor and shunt cores, instrument transformer cores and welding transformer cores. In short: standard EN grain-oriented grade; low loss along rolling direction; brittle, poorly formable strip.
What is the yield strength of M140-30P-SRA?
M140-30P-SRA has a typical yield strength of 295 MPa (42.8 ksi) and a tensile strength of 320 MPa (46.4 ksi) — weaker than 87% of steel grades.
Is M140-30P-SRA easy to machine?
Not especially — machinability is rated poor (30/100, worse than 89% of steel grades). Normally only slit, sheared, punched or laser/EDM cut to lamination shape — the Fe-3Si and its glass film are highly abrasive, so carbide tooling with tight clearance and frequent regrinding is required to limit burrs.
Can M140-30P-SRA be welded?
Not readily — weldability is rated poor (30/100). Avoid welding through the stack; TIG/laser tack welds break the interlaminar insulation and locally destroy the Goss texture, raising core loss — use clamping, banding or bonding instead.
What surface finishes work on M140-30P-SRA?
Supplied ready-coated (C-5 phosphate/forsterite or C-6 composite); do not pickle, blast or paint over it — protect cut edges against rust and handle to avoid scratching the insulating film.
Can M140-30P-SRA be formed, bent or molded?
Strip is brittle and strongly anisotropic; keep bends and core-winding radii generous, cut with the rolling direction along the flux path, and stress-relief anneal at ~800 °C in a protective atmosphere after forming.
What is the maximum service temperature of M140-30P-SRA?
M140-30P-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
- EN 10107 — Grain-oriented electrical steel strip and sheet delivered in the fully processed state — CEN (2014)
- GB/T 2521.2 — Cold-rolled grain-oriented electrical steel strip (30Q140 class) — SAC (2016)
- ASM Handbook Vol. 2 — Properties and Selection: Nonferrous Alloys and Special-Purpose Materials (magnetically soft materials) — ASM International (1990)
- Grain-oriented electrical steel product data (0.30 mm high-permeability grades) — GOES producers (e.g. thyssenkrupp Electrical Steel, Nippon Steel, Baosteel) (2023)
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.