Steel 30Q140-SRA (Stress-relief annealed)
Heat-treated state
EN 30Q140
Anneal wound or stamped cores after forming at about 800–840 °C in protective atmosphere to remove working stress and restore low core loss; hardness falls and added brittleness demands careful handling.
Values for the SRA condition
What is 30Q140-SRA?
30Q140-SRA is 30Q140 heat treated to SRA — anneal wound or stamped cores after forming at about 800–840 °C in protective atmosphere to remove working stress and restore low core loss; hardness falls and added brittleness demands careful handling. 30Q140-SRA has a yield strength of 290 MPa (42.1 ksi) and a tensile strength of 330 MPa (47.9 ksi) — weaker than 88% of steel grades. Elongation at break is 16% and the elastic modulus is 120 GPa (17.4 Msi). 30Q140-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 — 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 — 40/100, worse than 96% of steel grades
- Poor heat conductor — 23 W/m·K (13.3 BTU/hr·ft·°F), worse than 92% of steel grades
- Low strength — 290 MPa (42.1 ksi), worse than 88% of steel grades
30Q140-SRA properties
Typical room-temperature values for 30Q140-SRA; 6 are specific to this condition. Other listed values are 30Q140 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
30Q140-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).
Mechanical9
30Q140-SRA has a yield strength of 290 MPa (42.1 ksi) and a tensile strength of 330 MPa (47.9 ksi) — weaker than 88% of steel grades. Elongation at break is 16% and the elastic modulus is 120 GPa (17.4 Msi).
Thermal6
30Q140-SRA is rated for continuous service to 150°C (302 °F). It conducts heat at 23 W/m·K (13.3 BTU/hr·ft·°F), worse than 92% of steel grades. Thermal expansion is 11.8 µm/m·K (6.56 µin/in·°F).
Electrical3
30Q140-SRA conducts electricity at 3.6 % IACS, worse than 85% of steel grades.
Chemical & Environmental3
Corrosion resistance is poor (20/100), better than 87% of steel grades.
Sustainability4
Producing a kilogram of 30Q140-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%.
Manufacturability7
30Q140-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 30Q140-SRA
Is 30Q140 easy to machine?
Work is precision shearing, blanking and slitting; dies need carbide or coated edges and a clearance of about 5–8 % of thickness to limit burr height and the width of the shear-stressed zone.
Can 30Q140 be welded?
Avoid welding where possible; hold cores with clamping frames or banding, and if spot or TIG tacking is unavoidable, follow with a full stress-relief anneal — welds still raise loss locally.
Can 30Q140 be formed, bent or molded?
Suitable only for flat blanking and large-radius winding of wound cores; transverse bending cracks the strip. A stress-relief anneal at 800–840 °C in protective atmosphere after forming restores magnetic properties.
What surface finishes work on 30Q140?
Delivered with a C-5 type phosphate inorganic insulating coating and normally needs no further painting; sheared bare edges can be varnished or oiled to prevent rust.
30Q140 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 |
|---|---|---|
| Sikey element for Goss texture and high resistivity | 2.9 – 3.4 | 3.1 |
| Cresidual after decarburization annealing; lower means less aging | ≤ 0.01 | 0 |
| Mn | 0.03 – 0.2 | 0.1 |
| SMnS inhibitor residue | ≤ 0.01 | 0.01 |
| P | ≤ 0.03 | 0.02 |
| AlAlN inhibitor | ≤ 0.04 | 0.02 |
| N | ≤ 0.01 | 0.01 |
| Cuused as inhibitor element in some processes | ≤ 0.6 | 0.2 |
| Fe | balance |
30Q140-SRA — frequently asked
What is 30Q140-SRA used for?
30Q140-SRA is typically used for distribution transformer cores, reactor and choke cores, wound strip transformer cores, mitre-cut stacked core laminations and cut-to-length core sheet. In short: baseline grain-oriented transformer steel; low loss along rolling direction; not for formed parts.
What is the yield strength of 30Q140-SRA?
30Q140-SRA has a typical yield strength of 290 MPa (42.1 ksi) and a tensile strength of 330 MPa (47.9 ksi) — weaker than 88% of steel grades.
Is 30Q140-SRA easy to machine?
Not especially — machinability is rated fair (35/100, worse than 84% of steel grades). Work is precision shearing, blanking and slitting; dies need carbide or coated edges and a clearance of about 5–8 % of thickness to limit burr height and the width of the shear-stressed zone.
Can 30Q140-SRA be welded?
Not readily — weldability is rated poor (30/100). Avoid welding where possible; hold cores with clamping frames or banding, and if spot or TIG tacking is unavoidable, follow with a full stress-relief anneal — welds still raise loss locally.
What surface finishes work on 30Q140-SRA?
Delivered with a C-5 type phosphate inorganic insulating coating and normally needs no further painting; sheared bare edges can be varnished or oiled to prevent rust.
Can 30Q140-SRA be formed, bent or molded?
Suitable only for flat blanking and large-radius winding of wound cores; transverse bending cracks the strip. A stress-relief anneal at 800–840 °C in protective atmosphere after forming restores magnetic properties.
What is the maximum service temperature of 30Q140-SRA?
30Q140-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 — grain-oriented steel sheet and strip — IEC (2020)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels and High-Performance Alloys (Fe-Si electrical steels) — 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.