Study On The Microstructure And Properties Of(Cr-Ni)Non-oriented Silicon Steel With High Strength Produced By Twin-Roll Strip Casting

In recent years,due to the green house effect,the demand of environmentally friendly car is increasing.Japan is the first to produce the electric vehicle and hybrid electric vehicle.At present,these cars are becoming more and more popular in China.The heart of the electric vehicle and hybrid electric vehicle is the driving motor,which must satisfy the features of high-output,high-efficiency and miniaturization.Therefore,based on the idea of efficient use of magnetic torques,the IPM(Interior permanent magnet)motors,which the permanent magnets are embedded inside the rotor,are widely applied.Because of the high speed rotating and the rotor shape of the IPM,the silicon steel,which is used as the material of the rotor core,requires both good magnetic properties and high strength.Thus,the defomation and fatigue fracture caused by huge centrifugal forces can be prevented.The process of twin-roll thin strip continuous casting enjoys the features of short technology,low investment,energy efficiency and environmental protection.The rapid solidification can improve the good magnetic properties of texture {100}.This paper takes 3.2%Si non-oriented silicon steel as the research object.The Al?Mn?Cr?Ni are added as the alloying elements.The paper studies the effect of cold rolling ratio on the texture and magnetic properties of non-oriented silicon steel and the influence of the annealing process on the evolution of microstructure,texture and its performance.In addition,the influence of Ni on the texture of non-oriented silicon steel and its performance is also studied.The major work and achievements of the thesis are as follows:(1)The influence of cold-rolling reduction rate on microstructure,texture and magnetic properties is analyzed.When the cold-rolling reduction rate reaches 72%and 80%,a lot of shear zones are formed in the cold rolled sheets.When the rate gets to 89%and 92%,the shear zones have been pressed close to the level of fibrous tissue and the n?mber is decreasing.With the increase of the cold-rolling reduction rate,the strength of texture a and texture y go up.Under the same annealing condition,the thinner the finished board is,the lower the iron loss is.The level of the high frequency iron loss is especially great.(2)Effects of annealing temperature and time on the different thickness of the finished board texture,microstructure and properties have been studied as well.With the increase of the annealing temperature,texture ?,,texture ? and texture GOSS gradually become stronger,magnetic induction B50 grows,and the iron loss P15/50 becomes lower.However,P10/400?P10/800 and P10/1000o decreases at first and then increases.They reach the minim grain size at 900?.The yield strength decreases significantly.The grains are larger and the structure are most uniform at 900?.(3)When the annealing temperature reaches 750?,and the 0.5mm finished boards without Ni are annealed for 60 seconds,the magnetic and mechanical properties are updated.Finished boards of 0.35mm are annealed for 50 seconds,thus the magnetic and mechanical properties are relatively good.Finished boards are annealed for 32 seconds to 36 seconds,and the magnetic and mechanical properties can be updated.Moreover,the finished boards of 0.15mm are annealed for 24s to 28s,the magnetic and mechanical properties can be updated as well.(4)The effects of Ni on the microstructure and properties of the non-oriented silicon steel when one percent of Ni is added has been comparatively studied as well.Comparing with the steel,which does not contain Ni,the finished boards with Ni form stronger cube texture,Goss texture and weaker y texture.The size of grains are larger.As for the finished boards of 0.5mm,when annealed at 650? to 900? for 2 minutes,the magnetic properties of the finished boards with Ni is higher than that without Ni by over 0.01T,the P15/50 is lower to more than 0.5W/kg P10/400 lower by 1.0W/kg or more,?s is higher to 20MPa or more.The Ni can improve magnetic properties and increase the yield strength.(5)When the annealing temperature reaches 750? and being annealed for 60seconds,the magnetic and mechanical properties of the 0.5mm-thickness finished boards with Ni are updated.With the same technology,the magnetic induction of the finished boards with Ni is higher than those without Ni.The distinction is about 0.04T P15/50 lowers by 0.6W/kg and P10/400 lowers by 5.0W/kg,The yield strength is higher by 95MPa.As for the finished boards of 0.35mm,when annealed for 50s,the magnetic and mechanical properties are good.Comparing with the boards of the similar technology,the magnetic induction is higher than that of non-Ni finished boards.The distinction is 0.02T.P15/50 lowers by 2.2W/kg and P10/400 lowers by 13.4W/kg,P10/800 lowers by 10.7W/kg and P10/1000 lowers by 9.6W/kg.The yield strength is higher by 106MPa.The Ni can improve magnetic properties and increase the yield strength.