| Fe-6.5wt%Si alloy(also known as high silicon electrical steel)has excellent soft magnetic properties such as high permeability,low iron loss,low coercivity,and nearly zero magnetostriction coefficient.It is an ideal soft magnetic material for manufacturing electric equipment,electric vehicles,high-frequency electrical appliances,etc.However,due to the inherent brittleness of high silicon electrical steel,it is difficult to prepare high silicon electrical steel strip with a thickness of 0.1～0.3 mm on a large scale by traditional casting rolling forming method at present,which limits the wide application of high silicon electrical steel.In the previous research,our research group adopted various plasticizing methods such as microalloying,solidification structure orientation control,deformation,heat treatment,etc.,which significantly improved the brittleness of high silicon electrical steel,improved its deformation ability,and realized the laboratory preparation and processing of high silicon electrical steel strip.In this paper,based on the previous research of the research group,aiming at the problems that the existing microalloying elements still have limited effect on plastic lifting,have adverse effects on magnetic properties,and the existing directional solidification methods have low efficiency in preparing billets,the idea of comprehensively utilizing Nb microalloying and electroslag remelting to significantly improve the plastic deformation ability and machinability of high silicon electrical steel is proposed,The microstructure,ordered structure,mechanical properties and magnetic properties of high silicon electrical steel containing 0～0.50wt%Nb during the preparation process are mainly studied,which provides a technological basis for promoting the engineering application of the casting rolling forming technology of high silicon electrical steel.The main conclusions are as follows:The hot deformation behavior of high silicon electrical steel samples with different Nb content under the conditions of deformation temperature 800～1100℃,strain rate 0.01～10 s-1 and total deformation 50%was studied by hot compression experiment.The results show that the addition of Nb increases the hot deformation activation energy of high silicon electrical steel samples,inhibits the generation of microcracks during hot deformation,reduces the order of samples after hot compression,and is conducive to improving the warm rolling formability.The suitable thermal deformation conditions for Nb containing samples are 900～1100℃and the strain rate is 0.01～10 s-1.With the increase of Nb content,the plasticity of high silicon electrical steel increases gradually.When Nb content is increased from 0 to 0.50wt%,the average three-point bending fracture deflection of the warm rolled specimen at room temperature increases from 4.5 mm to 9.9 mm.The mechanism of Nb microalloying to improve the plasticity of warm rolled specimens includes three aspects:one is that the layered structure hinders crack growth and delays fracture;Second,a large number of fine Nb rich precipitates hinder grain growth and refine grains;Third,the formation of Nb rich precipitates destroyed the ordered rearrangement between adjacent Fe and Si atoms in the matrix,inhibited the ordered transformation of high silicon electrical steel samples during cooling,and reduced the degree of order.A large number of Nb rich phases with a size of about 100 nm were precipitated after annealing of cold rolled samples.When annealing-temperature is lower than 1200℃,fine Nb rich precipitates inhibit grain growth.When the annealing temperature is higher than 1200℃,the Nb rich precipitates dissolve,which makes the pinning force of precipitates relative to grain boundaries weaken,and the average grain size of the sample increases significantly.After annealing at 1200℃/1h,the sample has proper grain size and high comprehensive magnetic properties.Large size high silicon electrical steel ingots with columnar microstructure with high<001>orientation were prepared by electroslag remelting.Compared with the vacuum melting as-cast sample,the electroslag remelting sample has better bending deformation performance and warm-rolling workability,and can achieve the warm rolling forming of 90%of the total deformation without obvious edge cracks.The average elongation of the electroslag remelting-warm rolling sample at room temperature is about 2.9%,and the fracture morphology shows the characteristics of plastic deformation.The subsequent cold-rolling workability is significantly improved.The magnetic induction B8,B50,iron loss P10/50 and P10/100 of 0.2 mm electroslag remelting-warm rolling-cold rolling sample annealed at 1200℃/1h are 1.33 T,1.63 T,0.56 W/kg and 7.54 W/kg respectively.The comprehensive magnetic properties are superior to those of the strip produced by Japanese CVD industrial method with the same thickness. |
