Experimental Study On Eliminating Residual Stress Of Cold Rolled Sheet By Pulsed Magnetic Thermal Coupling Field

Residual stress formed during cold rolling of steel strip is an inevitable product of uneven plastic deformation,which will seriously affect the shape and size accuracy of the product,and also affect the magnetic properties of soft magnetic materials such as oriented silicon steel.Residual stress inside the material is closely related to dislocation proliferation caused by uneven plastic deformation.Heat treatment is the most widely used method to remove residual stress in production.Due to the drawbacks of this process,it has become one of the most energy consuming and pollution processes in the process of removing residual stress of cold rolled steel strip.As a clean,efficient and contactless physical field,pulsed magnetic field has been widely used in the field of removing residual stress of materials.The high frequency and high frequency strong magnetic fields are not conducive to industrial application.It will be an efficient and advanced method to enhance residual stress removal by using short-term,low-temperature and low-intensity pulsed magnetic-thermal coupling field.Using secondary cold-rolled silicon steel as experimental material,the effects of treatment time,treatment temperature and peak current on residual stress removal by magnetic-thermal coupling field were studied by three-factor and three-level orthogonal experiments.On this basis,the influence of magnetic-thermal coupling field on the reduction of dislocation density of cold-rolled silicon steel is studied.By establishing a model of magnetic-thermal coupling field to reduce residual stress of cold-rolled silicon steel,its removal mechanism is explained,and the optimal process of magnetic-thermal coupling field to remove residual stress is obtained.Short-time low-temperature heat treatment and short-time low-intensity pulsed magnetic field treatment can reduce the residual stress of cold-rolled silicon steel,the treatment effect is16.7% and 20%,respectively.Short-time,low-temperature and low-intensity pulsed magnetic-thermal coupling field treatment can effectively reduce the residual stress of cold-rolled oriented silicon steel.The optimal removal effect is 55.5%,3.3 times that of heat treatment alone,and 2.7 times that of pulse magnetic treatment alone.The orthogonal experimental results show that the three factors influencing the treatment temperature,peak current(magnetic field strength),and treatment time are from strong to weak.The maximum reduction in residual stress is perpendicular to the direction of the magnetic field.The optimum process for reducing residual stress and dislocation density in short time,low temperature and low intensity pulsed magnetic-thermal coupling field is 180 s,400 C,180 A.The maximum decrease of residual stress is 55.5%,(110),(200),(211)and the maximum decrease of dislocation density is 50.06%,62.77%,46.39%,respectively.The micro-mechanism of remnant stress removal by short-time,low-temperature and low-intensity pulsed magnetic-thermal coupling field process is that the application of low-intensity pulsed magnetic field on the basis of low-temperature thermal field further enhances the trend of dislocation motion in the material,achieves local recovery,and achieves the purpose of reducing the dislocation density and residual stress.