CRNGO Electrical Steel Grades for Home Appliance Motors and Compressors

What CRNGO Electrical Steel Means in Appliance Motors

Cold-rolled non-grain-oriented (CRNGO) electrical steel is the default magnetic material for the motors and small transformers inside household appliances. Silicon content usually falls between 0.5% and 3.0%; that addition raises electrical resistivity and suppresses eddy-current loss, while the non-oriented grain structure gives predictable magnetic behaviour in every direction of the lamination. Appliance motors see a rotating flux through the stator teeth and yoke, so isotropy is an advantage rather than a compromise.

Compressor motors, fan motors, drain pumps and timer motors in air conditioners, refrigerators and washing machines are almost all built from 0.35 mm or 0.50 mm CRNGO laminations, supplied in the fully processed state.

Typical CRNGO Grades Specified for Appliance Laminations

Grade designations follow the GB/T 2521.2-2016 and IEC 60404-8-4 convention: the first two digits give nominal thickness in hundredths of a millimetre, and the trailing digits give the maximum specific total loss at 1.5 T and 50 Hz in units of 0.01 W/kg. A 50W600 grade is therefore 0.50 mm material with a guaranteed maximum loss of 6.00 W/kg.

Buyers normally match the loss grade to the efficiency target of the finished appliance. Where the stamping press capacity allows, 0.35 mm stock cuts loss and stack height, but it also increases the number of laminations per core and the stamping cost per stack.

Why Non-oriented Steel Rather Than Grain-oriented Steel

Grain-oriented grades covered by IEC 60404-8-7 reach their lowest loss and highest permeability only along the rolling direction. In a stator, where flux rotates, that advantage largely disappears while the price premium remains. CRNGO also punches and stacks more predictably because there is no directional grain structure to shear, and it tolerates welding, cleating and interlocking into the finished stator core without a directional loss penalty.

Stamping, Coating and Core Loss Control

Laminations are produced by blanking or high-speed progressive stamping, followed by deburring and, where the application justifies it, stress-relief annealing. Surface insulation matters as much as the steel itself: a C5 or C6 type coating on GB/T 2521.2-2016 material provides the inter-laminar resistance that keeps eddy-current loss low after clamping. Burr height is generally controlled to a few hundredths of a millimetre depending on stack length, and interlocking features that plastically deform the steel locally raise loss in the affected zones, so die condition needs routine monitoring.

Magnetic Property Verification

Specific total loss and magnetic induction are verified with the Epstein frame method of IEC 60404-2 or the single-sheet tester of IEC 60404-3, at 50 Hz or 60 Hz. ASTM A677/A677M and JIS C 2552 are commonly quoted for export deliveries, while EN 10106 applies to European requirements and GB/T 2521.2-2016 to domestic Chinese supply. A practical incoming inspection plan checks thickness tolerance, coating adhesion, loss at 1.5 T, lamination factor and, for high-efficiency programmes, iron loss after annealing on a witness sample.

Frequently Asked Questions

Q: Which CRNGO grade is standard for a refrigerator compressor motor?
A: 50W600 or 50W470 in 0.50 mm thickness covers most hermetic compressor stators; 50W470 is selected when the compressor must meet a higher efficiency class.

Q: Does a silicon content above 3.0% improve appliance motor performance?
A: Not usually. Resistivity rises, which lowers eddy-current loss, but saturation induction falls and the material becomes harder to punch and more brittle. Most appliance grades sit between 0.5% and 2.0% silicon.

Q: Should I specify 0.35 mm or 0.50 mm thickness?
A: 0.50 mm gives the lowest cost per stack at 50 Hz. Choose 0.35 mm when the design needs lower loss at the same induction, a shorter stack, or operation at higher electrical frequency.

Q: Is stress-relief annealing required after stamping?
A: It is not mandatory, but it restores loss in the shear-affected zone and is common practice for premium-efficiency motors. Annealing temperature must stay below the level that damages the insulation coating.

Q: How is the insulation coating class chosen?
A: Match it to the annealing cycle and to the varnish dip temperature. A C5 coating survives stress-relief annealing; a C6 coating offers better weldability and stacking factor.

Q: How can I compare coils from two suppliers fairly?
A: Ask for a coil-by-coil loss record measured to IEC 60404-2 at a stated induction and frequency, plus thickness tolerance, lamination factor and coating type, instead of comparing nameplate grades alone.