ELECTRICAL STEELS

1478112 Silicon-free steel BRITISH STEEL CORP 24 Sept 1974 [24 Sept 19731 44702/73 Headings C7A and C7D [Also in Division B3] Non silicon steel for electromagnetic applications containing 0À35-0À9% Mn and less than 0À05% Si with properties equivalent to conventionally prepared steels containing up to 2% Si is made by subjecting conventionally refined i.e. open hearth basic oxygen or other steel to vacuum degassing to reduce the carbon content to 0À02% or less, adjusting the P contents to 0À05-0À15% by the addition of, say, ferrophosphorus, followed by casting and hot-rolling at a finishing temperature of 1550-1850‹F. Primary cold-rolling to within 5-15% of final gauge is followed by a non- decarbonizing anneal in a box furnace at 1220- 1300‹F in a 4% hydrogen/nitrogen mixture to keep a 'bright' surface before finally cold-rolling to size. Laminates for the cores of electrical machines may be machined or punched out, and after stacking, a further decarbonizing anneal may be given to further improve the magnetic properties. A typical steel contains 0À004- 0À02%C 0À35 - 0À90%Mn 0À07 - 0À15%P 0À01 max Al 0À04 max Oxygen Bal Iron and unavoidable impurities.