What is non grain oriented electrical steel used for?

 

 

 

 

NGO electrical steel, also called non-oriented silicon steel, is a soft magnetic alloy in which silicon (typically about 0.5–3.2% by mass) is the main alloying element and carbon is kept extremely low (usually no more than about 0.005%). The low carbon level and the silicon addition reduce hysteresis loss and raise electrical resistivity, which together cut the energy lost as heat when the material is magnetised in an alternating field.

 

"Non-grain-oriented" means the crystal grains have no preferred rolling direction, so the magnetic properties-permeability and core loss-are essentially isotropic, i.e. the same in any in-plane direction.

 

Because of this isotropy, NGO steel is the natural choice wherever the magnetic flux rotates inside the core, which is the situation in every rotating electrical machine. By contrast, grain-oriented (GO) steel is processed so that most grains are aligned with the rolling direction; it offers lower core loss and higher flux density, but only in one direction, which suits static transformer cores rather than rotating machines.

 

 

NGO electrical steel is purchased almost exclusively as slit strip or as stamped laminations for the following families of application:

Application area	Typical parts	Notes
Motors (medium and small)	Stator and rotor lamination stacks of AC induction motors, permanent-magnet synchronous motors and DC motors	Dominant use of NGO steel; lamination stacks reduce eddy-current loss in the rotating flux field
Generators	Stator and rotor cores of small and medium generators, including portable and standby units	Same rotating-flux logic as motors; isotropic properties keep loss uniform
Small transformers and reactors	Core laminations of small distribution transformers, instrument transformers and reactor cores	Where cost and punching ease matter more than the lowest possible no-load loss; large power transformers use GO steel instead
Relays and contactors	Magnetic circuits, armatures and yokes	Low-carbon NGO grades punch cleanly and magnetise quickly
Household appliance motors	Compressor motors, fan motors, washing-machine and vacuum motors	High-volume stamping with tight dimensional tolerances; standard and semi-processed grades both used
Electric-vehicle drive motors	High-frequency stator cores of traction motors	Higher-grade NGO (thin gauge, low core loss at 400 Hz and above) is typical; not every supplier carries these grades

Application mapping follows common engineering practice and the scope definitions of the NGO standards cited in this article; confirm grade selection with the supplier and the applicable standard before ordering.

 

 

 

NGO steel is supplied as fully processed or semi-processed strip, normally 0.35–0.65 mm thick for standard motor work. Grade names encode thickness and core loss. In the Chinese designation 50W470 (GB/T 2521.1), "50" means 0.50 mm nominal thickness, "W" marks non-oriented steel, and "470" stands for a guaranteed maximum core loss of 4.70 W/kg measured at 1.5 T, 50 Hz (P1.5/50).

 

The equivalent designation in EN 10106 is M470-50A (fully processed, 0.50 mm, 4.7 W/kg class). ASTM A677 covers fully processed non-oriented electrical steel with a similar classification logic (grade numbers based on thickness and guaranteed core loss at 15 kG / 60 Hz).

 

Designation	Thickness	Core loss P1.5/50 (max)	Flux density	Standard
50W470	0.50 mm	4.70 W/kg	B50 ≥ 1.65 T	GB/T 2521.1 (typical grade values per the standard)
M470-50A	0.50 mm	4.70 W/kg	B2500 ≥ 1.67 T	EN 10106 (fully processed)
Comparable ASTM A677 types	0.47–0.50 mm	Guaranteed core loss class at 15 kG / 60 Hz	Induction per A677 grade table	ASTM A677 (fully processed non-oriented)

Reference values above are standard guaranteed figures used for material selection; the exact figures on a mill certificate may be tighter. Always verify against the current edition of the standard (e.g. GB/T 2521.1-2016) and the supplier's test certificate. Semi-processed (e.g. M470-50S in EN 10106) grades are also available for customers who anneal after stamping.

 

 

Buyers frequently confuse non-grain-oriented and grain-oriented electrical steel because both are sold as "silicon steel". The selection rule is simple: rotating machines take NGO steel, static transformer cores take GO steel.

Property	Non-grain-oriented (NGO)	Grain-oriented (GO)
Grain structure	Random orientation, isotropic magnetic properties	Grains aligned with rolling direction (Goss texture)
Core loss	Higher; typical standard grades e.g. 4.70 W/kg at 1.5 T / 50 Hz (50W470, M470-50A)	Lower; e.g. 0.23 mm grades at 0.75–0.85 W/kg at 1.7 T / 50 Hz (typical high-grade values, e.g. 23RK075 per this site's published data)
Flux density	B50 typically ≥ 1.6 T (per GB/T 2521.1)	B8 typically ≥ 1.8 T (high-permeability grades, per GB/T 2521.2)
Magnetic behaviour	Same in all in-plane directions	Best along rolling direction, poor across it (anisotropic)
Typical applications	Motor and generator cores, small transformer/reactor cores, relays, appliance motors	Power and distribution transformer cores, where flux follows one direction
Governing standards	GB/T 2521.1, EN 10106, ASTM A677	GB/T 2521.2, EN 10107, ASTM A876

 

 

The standard manufacturing route for fully processed NGO steel follows six stages:

• Steelmaking and continuous casting - low-carbon iron is alloyed with silicon and melted in a converter or electric arc furnace, then cast into slabs.
• Hot rolling - slabs are rolled into strip; the hot-rolled coil is the starting point for the finished product.
• Pickling - scale is removed from the hot-rolled surface before cold rolling.
• Cold rolling - the strip is reduced to final gauge (typically 0.35–0.65 mm for motor grades).
• Final annealing - recrystallisation annealing develops the random grain structure that gives NGO steel its isotropic magnetic properties.
• Insulating coating and slitting - an inorganic or semi-organic insulation coating is applied to keep eddy-current loss low in the finished stack, and the strip is slit to width for stamping.

 

Customers receive the material as coils, slit coils or pre-stamped laminations; the lamination stacks are then welded, bonded or clamped into motor stators and rotors or small transformer cores.

 

 

FAQ

Q1. Is NGO electrical steel used in transformers?

Yes, but only in limited roles. NGO steel appears in small distribution transformers, instrument transformers and reactor cores where punching ease and cost matter more than the lowest no-load loss. Large power transformers use grain-oriented (GO) steel, because their cores operate with flux essentially aligned to one direction, which is exactly the condition where GO steel's anisotropic advantage applies.

 

Q2. What does the grade name 50W470 mean?

In the Chinese standard GB/T 2521.1, 50W470 means: nominal thickness 0.50 mm ("50"), non-oriented steel ("W"), and a guaranteed maximum core loss of 4.70 W/kg measured at 1.5 T and 50 Hz ("470"). The EN 10106 equivalent is M470-50A, where "A" denotes fully processed material.

 

Q3. Why is NGO steel chosen for motors and GO steel for transformers?

In a motor or generator, the flux direction in the core rotates as the shaft turns, so the core material must behave the same in every direction - that is what NGO steel's isotropic structure provides. In a transformer, flux follows a fixed loop, so the mill can align grains in that single direction and cut core loss further; GO steel delivers that benefit but is highly anisotropic, which makes it unsuitable for rotating cores.

 

Q4. How thin does NGO electrical steel come?

Standard motor grades are supplied in 0.35–0.65 mm thickness. Thinner gauges (down to about 0.2 mm and below) exist for higher-frequency duty such as EV traction motors, where eddy-current loss grows with frequency; these grades carry their own designation series and are quoted separately by suppliers.

 

In summary, non-grain-oriented electrical steel is the workhorse core material for rotating electrical machines - motors first, then generators, small transformer and reactor cores, relays and appliance drives. Its isotropic magnetic behaviour, expressed through grade designations such as 50W470 (GB/T 2521.1) and M470-50A (EN 10106), lets engineers predict core loss in every operating direction, which is precisely what a rotating machine demands. Buyers who match the application, the grade and the governing standard will get predictable performance from every coil.

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