Effect of Mn on hot deformation behavior of medium grade non-oriented silicon steel without normalizing process
The energy saving,low carbon emission and low-cost production will be come true when there is no nor-malization in the process of non-oriented electrical steel.This need to be optimal alloying design,Mn element could be a potential option.However,at present,the role of Mn element in the hot deformation of non-oriented electrical steel still needs comprehensive understanding.The effect of Mn on the hot deformation behavior of 1.5%Si-0.3%Al medium grade non-oriented electrical steel was investigated by the methods of thermodynamic phase dia-gram calculation,thermal simulation and microstructural characterization experiments.Rheological peak stress con-stitutive equations of specimens with different Mn content have been established and the critical strains of dynamic recrystallization in specimens have been calculated on the basis of constitutive equations.The grain size and volume fraction of recrystallization in specimens with different Mn content was also analysed.The results show that the more the Mn content,the higher the activation energy,in addition,the flow stress of specimens increased with the increase of Mn content on the same deformation condition,while,the ratio of critical strain to peak strain for dynamic recrystallization decreased.Moreover,the volume fraction of dynamic recrystallization in specimens improved with the increase of Mn content.It means that Mn element can promote the occurrence of dynamic recrystallization,which is beneficial for the production of non-oriented silicon steel without normalizing process.At the range of hot deforma-tion temperatures,austenite phases in specimens increased with the increase of Mn content and the solid solution atoms in specimens increased too.This brings,on one hand,more harder austenite phases which offer more resis-tance to hot deformation,so the higher activation energy and flow stress are obtained.On the other hand,dislocations are less mobile and relative difficulty to climb or cross slip at high temperatures owing to the low stacking-fault energy in austenite and dynamic recovery is limited.Thus,deformation storage energy can be effectively accumu-lated.Besides,higher lattice distortion energy due to more solid solution Mn atoms can also hinder dislocations movement effectively which is also beneficial for the accumulation of deformation storage energy.Consequently,the occurrence of dynamic recrystallization took place more fully in specimens with more Mn content.
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