The earliest process to manufacture Cold Rolled Grain Oriented Electrical Steel, popularly known as CRGO, was first patented 70 years ago in 1933 in USA. The earliest grades of CRGO were known as M10, (approx. 1.00 watts/lb. at 1.5T/60Hz) and M9 (approx.0.90 watts/lb. at 1.5T/60Hz).
By 1947, the first catalog containing design curves and other essential information on grain oriented steels was published.
In 1955, grades M7 (approx.0.7w/lb at 1.5T/60Hz) and M6 (approx.0.6w/lb at 1.5T/60Hz) were developed and were the most widely used grades of CRGO.
However, the first Conventional Grain Oriented Steel (CGOS) grades known popularly today as M3, M4 and M5 were developed in the late sixties and the Hi-B Grain Oriented Steel grades (HG-OS) were developed in the early seventies whilst laser scribed material in the mid-eighties.
ARMCO, USA, (now known as A.K. Steel) were the pioneers in the development of CGOS grades whilst the Japanese mills Nippon Steel and Kawasaki Steel, the pioneers in the development of HGO grades and laser scribed grades.
In the development of Grain Oriented Steels over the past 70 years, not only have the hystereses losses been significantly reduced from the earliest grades of GO developed, but the thickness has been significantly reduced, thereby reducing the eddy current losses. The insulation coating has been significantly improved to keep interlaminar losses at a minimum.