Rapidly solidified high silicon steel with minor boron addition that improves magnetic properties

Abstract

Fe-6.5% Si electrical steel is alloyed with boron to reduce its melting temperature and interfacial energy to improve processability for melt-spinning applications. Boron additions from 0.01 wt % to 2.24 wt % into Fe-6.5% Si and its effect on ribbon thickness, grain size, magnetic, and mechanical properties are disclosed. Minor boron alloying significantly changed the melt pool stability and wetting on a melt-spinning quench wheel and in turn increased the quench rate with minimum impact on the magnetic saturation and ductility. Boron addition of less than 0.06 wt % was also found beneficial to the magnetic property of the alloy by lowering both its hysteresis and eddy current losses.

What is claimed is: 
     
         1 . A method of preparing a ribbon of electrical steel comprising 6.5 wt % Si, the method comprising:
 directing a stream of the electrical steel in a molten form onto an outer surface of a rotating wheel;   cooling the stream of electrical steel on the outer surface of the rotating wheel to form the ribbon; and   spinning the ribbon off of the outer surface of the rotating wheel;   wherein the ribbon comprises a thickness as measured perpendicular to the outer surface, the thickness being 0.1 mm or less; and   wherein the electrical steel comprises from 100 ppm to 2100 ppm of B.   
     
     
         2 . The method of  claim 1 , wherein the ribbon of electrical steel comprises a saturation magnetization of at least 17.6 kG (1400 kA/m). 
     
     
         3 . The method of  claim 1 , wherein the ribbon of electrical steel comprises a Vickers hardness (HV) in a range from 300 to 500. 
     
     
         4 . The method of  claim 1 , wherein, under a maximum magnetic flux density of 10 kG (1 T) with excitation source in direct current mode, a maximum permeability (p max ) of the ribbon of electrical steel is greater than 1000. 
     
     
         5 . The method of  claim 1 , wherein, under a maximum magnetic flux density of 10 kG (1 T) with excitation source in direct current mode, coercivity (H c ) of the ribbon of electrical steel is less than 0.7 Oe (55 A/m). 
     
     
         6 . The method of  claim 1 , wherein, under a maximum magnetic flux density of 10 kG (1 T) with excitation source in an alternating current mode at a frequency of 400 Hz, an iron loss of the ribbon of electrical steel is 12 W/kg or less. 
     
     
         7 . The method of  claim 1 , wherein the ribbon of electric steel comprises about 14 wt % or less of Fe—Si—B eutectic phase. 
     
     
         8 . The method of  claim 1 , wherein the ribbon of electrical still comprises from 500 ppm to 1500 ppm of B. 
     
     
         9 . The method of  claim 1 , wherein the ribbon comprises a length of at least 10 m. 
     
     
         10 . The method of  claim 1 , wherein the ribbon comprises a width in a range from 1 mm to 300 mm. 
     
     
         11 . An electrical steel structure, comprising:
 a ribbon having a length, a width, and a thickness, the length being perpendicular to the width and the thickness being perpendicular to both the length and the width;   wherein the ribbon comprises Fe-6.5% Si and 100 ppm to 2100 ppm of B; and   wherein the thickness of the ribbon is 0.1 mm or less.   
     
     
         12 . The electrical steel structure of  claim 11 , wherein the ribbon comprises a magnetic saturation of at least 17.6 kG (1400 kA/m). 
     
     
         13 . The electrical steel structure of  claim 11 , wherein the ribbon comprises a Vickers hardness (HV) in a range from 300 to 500. 
     
     
         14 . The electrical steel structure of  claim 11 , wherein, under a maximum magnetic flux density of 10 kG (1 T) with excitation source in direct current mode, a maximum permeability (μ max ) of the ribbon is greater than 2000. 
     
     
         15 . The electrical steel structure of  claim 11 , wherein, under a maximum magnetic flux density of 10 kG (1 T) with excitation source in direct current mode, coercivity (H c ) of the ribbon is less than 0.7 Oe (55 A/m). 
     
     
         16 . The electrical steel structure of  claim 11 , wherein, under a maximum magnetic flux density of 10 kG (1 T) with excitation source in an alternating current mode at a frequency of 400 Hz, an iron loss of the ribbon is 12 W/kg or less. 
     
     
         17 . The electrical steel structure of  claim 11 , wherein the ribbon comprises about 14 wt % or less of Fe—Si—B eutectic composition. 
     
     
         18 . An electrical component comprising a plurality of layers of the electrical steel structure according to  claim 11  arranged in a stack. 
     
     
         19 . The electrical component of  claim 18 , wherein the electrical component comprises at least a part of a stator or a rotor of an electric motor or at least a part of a core of a transformer. 
     
     
         20 . The electrical component of  claim 18 , further comprising a plurality of layers of insulation in the stack, wherein a layer of insulation is provided between every one to ten layers of the electrical steel structure. 
     
     
         21 . The electrical component of  claim 20 , wherein the electrical component comprises at least part of a stator or rotor of an electric motor or at least part of a core of a transformer.