Steel M43-SP (Semi-processed, as-rolled)
Finish state · default condition
AISI/SAE M43 · UNS T11343
Standard stocked condition for stamped lamination stacks: punch first, then anneal to develop core loss.
Values for the SP condition
Other M43 tempers and conditions
M43 is listed in 5 conditions; see the grade overview at M43.
Compare all 5 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Quality (decarburising/grain-growth) annealed after punching | Condition after the ~790–840 °C customer anneal — pick when magnetic performance (core loss ≈ 4.3 W/lb at 1.5 T, 60 Hz) is the design driver. | 270 | 420 | 30 | 110 HB | 4.1 % IACS |
SPDefaultThis page Semi-processed, as-rolled | Standard stocked condition for stamped lamination stacks: punch first, then anneal to develop core loss. | 315 | 450 | 20 | 130 HB | 4.1 % IACS |
Annealed | As-supplied soft bar of the M43 high-speed steel (≈1.2C-8Mo-8Co-3.75Cr-1.6V-2.75W) for machining tool blanks before hardening. | 600 | 900 | 10 | 24 HRC | 22 W/m·K |
Hardened & triple tempered | Maximum-hardness condition (≈1190–1210 °C austenitise, 540–560 °C triple temper) for drills, end mills and form tools cutting high-strength or abrasive alloys. | — | 2,100 | 0.5 | 68 HRC | 24 W/m·K |
Hardened & tempered | Slightly softer temper for interrupted cuts, taps and broaches where edge chipping is the failure mode. | 2,100 | 2,350 | 0.5 | 66 HRC | 3.1 % IACS |
What is M43-SP?
M43-SP is M43 supplied in the SP condition — standard stocked condition for stamped lamination stacks: punch first, then anneal to develop core loss. M43-SP has a yield strength of 315 MPa (45.7 ksi) and a tensile strength of 450 MPa (65.3 ksi) — weaker than 82% of steel grades. Elongation at break is 20% and the elastic modulus is 200 GPa (29 Msi). M43-SP has a density of 7.8 g/cm³ (0.282 lb/in³), lighter than 87% of steel grades. It melts at 1,490°C (2,714 °F).
Advantages
- Forms and bends easily — 65/100, better than 81% of steel grades
Limitations
- Limited service temperature — 200°C (392 °F), worse than 93% of steel grades
- Poor heat conductor — 27 W/m·K (15.6 BTU/hr·ft·°F), worse than 86% of steel grades
- Low electrical conductivity — 4.1 % IACS, worse than 83% of steel grades
- Low strength — 315 MPa (45.7 ksi), worse than 82% of steel grades
M43-SP properties
Typical room-temperature values for M43-SP; 19 are specific to this condition. Other listed values are M43 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
M43-SP has a density of 7.8 g/cm³ (0.282 lb/in³), lighter than 87% of steel grades. It melts at 1,490°C (2,714 °F).
Mechanical12
M43-SP has a yield strength of 315 MPa (45.7 ksi) and a tensile strength of 450 MPa (65.3 ksi) — weaker than 82% of steel grades. Elongation at break is 20% and the elastic modulus is 200 GPa (29 Msi).
Thermal6
M43-SP is rated for continuous service to 200°C (392 °F). It conducts heat at 27 W/m·K (15.6 BTU/hr·ft·°F), worse than 86% of steel grades. Thermal expansion is 11.6 µm/m·K (6.44 µin/in·°F).
Electrical3
M43-SP conducts electricity at 4.1 % IACS, worse than 83% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (14/100), better than 70% of steel grades.
Sustainability4
Producing a kilogram of M43-SP takes about 32 MJ of energy and emits 2.3 kg of CO₂ — more than 70% of steel grades. Typical recycled content is 30%.
Manufacturability7
M43-SP's machinability is fair (45/100, worse than 65% of steel grades); weldability good (55/100); formability good (65/100).
Common Calculations5
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with M43-SP
Is M43 easy to machine?
Electrical-steel form is best blanked/punched with carbide dies (Si is abrasive, burr control critical); the HSS form must be machined in the annealed state and finished by grinding after hardening.
Can M43 be welded?
Avoid welding through electrical laminations — the HAZ loses permeability and raises core loss; HSS M43 is only welded by careful preheated TIG/laser repair on cutting edges.
Can M43 be formed, bent or molded?
Semi-processed sheet punches and stacks well, then requires a 790–840 °C anneal in a decarburising atmosphere to develop core loss; HSS is forged 1050–1150 °C then slow annealed at 870–900 °C.
What surface finishes work on M43?
Laminations rely on the mill C-3/C-5 insulating coating or dip varnish for interlaminar resistance; HSS tools are typically steam-oxide, nitride or TiN/TiAlN coated.
M43 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 |
|---|---|---|
| CA683 Type M43 electrical steel: chemistry not specified by the standard; typical mill analysis | ≤ 0.03 | 0.02 |
| Siprimary resistivity/loss control element | 1.7 – 2.5 | 2.1 |
| Al | 0.15 – 0.5 | 0.3 |
| Mn | 0.15 – 0.5 | 0.3 |
| P | ≤ 0.03 | 0.02 |
| S | ≤ 0.02 | 0.01 |
| Fe | balance | — |
M43-SP — frequently asked
What is M43-SP used for?
M43-SP is typically used for small motor lamination stacks, appliance motor stators and rotors, fractional-horsepower motor cores, solenoid and relay laminations, ballast and small transformer cores and cutting and form tools (high-speed steel variant). In short: semi-processed lamination steel; requires customer anneal; low-cost stamping grade.
What is the yield strength of M43-SP?
M43-SP has a typical yield strength of 315 MPa (45.7 ksi) and a tensile strength of 450 MPa (65.3 ksi) — weaker than 82% of steel grades. Strength varies by condition: see the 5 listed tempers.
Is M43-SP easy to machine?
Reasonably — machinability is rated fair (45/100, worse than 65% of steel grades). Electrical-steel form is best blanked/punched with carbide dies (Si is abrasive, burr control critical); the HSS form must be machined in the annealed state and finished by grinding after hardening.
Can M43-SP be welded?
Yes — weldability is rated good (55/100). Avoid welding through electrical laminations — the HAZ loses permeability and raises core loss; HSS M43 is only welded by careful preheated TIG/laser repair on cutting edges.
What surface finishes work on M43-SP?
Laminations rely on the mill C-3/C-5 insulating coating or dip varnish for interlaminar resistance; HSS tools are typically steam-oxide, nitride or TiN/TiAlN coated.
Can M43-SP be formed, bent or molded?
Semi-processed sheet punches and stacks well, then requires a 790–840 °C anneal in a decarburising atmosphere to develop core loss; HSS is forged 1050–1150 °C then slow annealed at 870–900 °C.
What is the maximum service temperature of M43-SP?
M43-SP 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.
What is the difference between M43-SP and M43 HSS-A?
SP is the default condition — standard stocked condition for stamped lamination stacks: punch first, then anneal to develop core loss. HSS-A: as-supplied soft bar of the M43 high-speed steel (≈1.2C-8Mo-8Co-3.75Cr-1.6V-2.75W) for machining tool blanks before hardening. Yield strength is 315 MPa in SP versus 600 MPa in HSS-A.
Sources
- ASTM A683 — Nonoriented Electrical Steel, Semiprocessed Types — ASTM International (2019)
- ASTM A677 — Fully Processed Nonoriented Electrical Steel — ASTM International (2019)
- ASTM A600 / SAE J438 — High-Speed Tool Steels (M43, UNS T11343) — ASTM International / SAE (2016)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels and High-Performance Alloys — ASM International (1990)
- ASM Specialty Handbook — Tool Materials — ASM International (1995)
- Non-oriented electrical steel lamination datasheets (M-grade core loss/mechanical data) — Cleveland-Cliffs (AK Steel) (2021)
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.