The invention discloses a
chromium-free semi-organic insulating
coating suitable for Bi-containing ultrahigh magnetic induction oriented
silicon steel without a bottom layer. The
chromium-free semi-organic insulating
coating is prepared from the following raw materials in percentage by weight: 15 to 25 percent of
phosphate aqueous solution, 1 to 15 percent of
colloidal silicon dioxide or colloidalaluminum
oxide or
titanium dioxide, 30 to 60 percent of organic resin, 0.5 to 5 percent of
metal oxide and the balance of water, wherein in the
phosphate aqueous solution, the content of
phosphate is33%, and positive ions are any one or more of Mg, Al, Ca, Zn and Na; in the
metal oxide,
metal cations are any one or more of Mn, Co, Ni, Al, Ca and Na. After being coated, the
coating is dried at the temperature of 300-500 DEG C, resin on the
surface layer of a steel plate is segregated, an insulating film cannot be damaged, the coating is good in
welding performance, and when the
welding speedis 80-120 cm / min, bubbles and air holes are not generated at a weld joint.