Process of making electrical steels

Abstract

Batch annealed, semi-processed and fully processed motor lamination steels are made by processes which subject a slab having an ultra low carbon composition (less than 0.01%) to at least the following steps: hot rolling with an austenite finishing temperature, coiling at a temperature ranging from 1300 DEG -1450 DEG F., and light temper rolling (less than 1.0% reduction) or leveling; reheating at a temperature less than 2300 DEG F., hot rolling with a ferrite finishing temperature, coiling at a temperature less than 1200 DEG F., and light temper rolling or leveling; or hot rolling with a ferrite finishing temperature, coiling at a temperature ranging from 1100 DEG -1350 DEG F. without a subsequent hot band anneal, and light temper rolling or leveling.

What is claimed is: 
     
       1. A method of making electrical steel strip characterized by low core loss and high permeability comprising the steps of: producing a slab with a composition consisting essentially of (% by weight):   ______________________________________                                    
       C:          up to 0.01                                             
       Si:         0.20-1.35                                              
       Al:         0.10-0.45                                              
       Mn:         0.10-1.0                                               
       S:          up to 0.015                                            
       N:          up to 0.006                                            
       Sb:         up to 0.07                                             
       Sn:         up to 0.12.Iadd., and                                  
       .Iadd.the balance being substantially iron,.Iaddend.               
______________________________________                                    
       hot rolling the slab into a strip with a finishing temperature in the austenite region;   coiling the strip at a temperature ranging from 1300°-1450° F.;   followed by the sequential steps of annealing the strip, cold rolling the strip, batch annealing the strip, and temper rolling the strip, wherein said temper rolling reduces the thickness of the strip by an amount ranging from about 0.25 to about 0.6% and the strip has a permeability when stress relief annealed of at least 2500 Gauss/Oersted.   
     
     
       2. The method of claim 1 wherein said step of temper rolling is carried out with a reduction in thickness ranging from about 0.25 to 0.5%. 
     
     
       3. The method of claim 1 further comprising stress relief annealing the strip. 
     
     
       4. The method of claim 3 wherein said temper rolling step is carried out at a reduction in thickness ranging from about 0.25 to 0.5%. 
     
     
       5. The method of claim 1 wherein a coil of the strip is heated during said batch annealing at a coil temperature of less than 1350° F. 
     
     
       6. The method of claim 1 wherein said permeability is obtained at an induction of less than about 1.5 Tesla. 
     
     
       7. The method of claim 1 wherein the strip has a core loss when stress relief annealed of not greater than 0.13 watts/pound/mil. 
     
     
       8. A method of making electrical steel strip characterized by low core loss and high permeability comprising the steps of: producing a slab with a composition consisting essentially of (% by weight):   ______________________________________                                    
       C:          up to 0.01                                             
       Si:         0.20-1.35                                              
       Al:         0.10-0.45                                              
       Mn:         0.10-1.0                                               
       S:          up to 0.015                                            
       N:          up to 0.006                                            
       Sb:         up to 0.07                                             
       Sn:         up to 0.12.Iadd., and                                  
       .Iadd.the balance being substantially iron,.Iaddend.               
______________________________________                                    
       reheating the slab at a temperature ranging from 2100°-2275° F.;   hot rolling the slab into a strip with a finishing temperature in the ferrite region;   coiling the strip at a temperature less than 1200° F.;   followed by the sequential steps of annealing the strip, cold rolling the strip, batch annealing the strip, and temper rolling the strip, wherein said temper rolling reduces the thickness of the strip by an amount ranging from about 0.25 to about 0.6% and the strip has a permeability when stress relief annealed of at least 2500 Gauss/Oersted.   
     
     
       9. The method of claim 8 wherein said step of temper rolling is carried out with a reduction in thickness ranging from about 0.25 to 0.5%. 
     
     
       10. The method of claim 8 wherein said step of coiling is carried out at a temperature of about 1000° F. 
     
     
       11. The method of claim 8 wherein said step of reheating the slab is carried out at a maximum preheat temperature of 2105° F., a maximum heating temperature of 2275° F., and a maximum soak temperature of 2275° F. 
     
     
       12. The method of claim 8 wherein said finishing temperature ranges from 1500°-1650° F. 
     
     
       13. The method of claim 8 including the step of stress relief annealing the strip after temper rolling. 
     
     
       14. The method of claim 13 wherein said temper rolling step is carried out at a reduction in thickness ranging from about 0.25 to 0.5%. 
     
     
       15. A method of making electrical steel strip without a hot band anneal characterized by low core loss and high permeability, comprising the steps of: producing a slab with a composition consisting essentially of (% by weight):   ______________________________________                                    
       C:          up to 0.01                                             
       Si:         0.20-1.35                                              
       Al:         0.10-0.45                                              
       Mn:         0.10-1.0                                               
       S:          up to 0.015                                            
       N:          up to 0.006                                            
       Sb:         up to 0.07                                             
       Sn:         up to 0.12.Iadd., and                                  
       .Iadd.the balance being substantially iron,.Iaddend.               
______________________________________                                    
       hot rolling the slab into a strip with a finishing temperature in the ferrite region;   coiling the strip at a temperature less than 1200° F.;   followed by cold rolling the strip, batch annealing the strip, and temper rolling the strip, wherein said temper rolling reduces the thickness of the strip by an amount ranging from about 0.25 to about 0.6%, and the strip has a permeability when stress relief annealed of at least 2500 Gauss/Oersted.   
     
     
       16. The method of claim 15 further comprising the step of stress relief annealing the strip. 
     
     
       17. The method of claim 16 wherein said temper rolling step is carried out at a reduction in thickness ranging from about 0.25 to 0.5%. 
     
     
       18. A method of making electrical steel strip characterized by low core loss and high permeability comprising the steps of: hot rolling a slab into a strip having a composition consisting essentially of (% by weight):   ______________________________________                                    
       C:          up to 0.01                                             
       Si:         0.20-1.35                                              
       Al:         0.10-0.45                                              
       Mn:         0.10-1.0                                               
       S:          up to 0.015                                            
       N:          up to 0.006                                            
       Sb:         up to 0.07                                             
       Sn:         up to 0.12.Iadd., and                                  
       .Iadd.the balance being substantially iron,.Iaddend.               
______________________________________                                    
       followed by coiling the strip, cold rolling the strip and batch annealing the strip, and then flattening the strip with a leveling process, wherein the strip has a thickness that has been reduced by said leveling process by an amount ranging from about 0.25 to about 0.6% and the strip has a permeability when stress relief annealed of at least 2500 Gauss/Oersted.   
     
     
       19. The method of claim 18 wherein said tension leveling elongates the strip by an amount ranging from about 0.25 to about 0.5%. 
     
     
       20. The method of claim 18 wherein the slab is hot rolled with a finishing temperature in the ferrite region. 
     
     
       21. The method of claim 18 wherein the slab is hot rolled with a finishing temperature in the austenite region, and the strip is coiled at a temperature ranging from 1300°-1450° F. and annealed between the pickling and cold rolling steps. 
     
     
       22. The method of claim 18 wherein the slab is reheated at a temperature less than 2300° F. and hot rolled with a finishing temperature in the ferrite region, and the strip is coiled at a temperature less than 1200° F. and annealed between the pickling and cold rolling steps. 
     
     
       23. The method of claim 19 further comprising stress relief annealing the strip.