Research On Cleanless Of Non-oriented Silicon Steel W800during Production Process

Clean steel is an important development direction in the future of steel，and it hasan important impact on non-oriented silicon steel product quality and magnetic；Improving the cleanliness of molten steel，control the precipitation and harmlesstreatment of inclusion is need to solve in non-oriented silicon steel-makingprocess.Therefore，in a domestic steel plant with hot metal treatment-210tBOF and Arstation-RH-continuous casting of W800non-oriented silicon steel rolling productionprocess，systematic sampling，using oxygen nitrogen analyzer，scanning electronmicroscope，large sample electrolysis to study the cleanliness of evolution in，steelmaking process，and the thermodynamics and kinetics of precipitation in steel MnS，AlN the analysis comes to the following conclusions：(1) W800steel C，Si，Mn，P，S and other elements are controlled in the requiredrange，arsenic，antimony，tin，copper，nickel in steel is almost constant in the smeltingprocess.(2) The T[O] gradually reduce and the nitrogen content gradually increased fromtapping to casting. Slab T[O] and nitrogen content were controlled at13.40×10-6，19.62×10-6.T[O] on the slab thickness direction and the maximum nitrogen content of at1/4, the bottom is minimum.Molten secondary oxidation occurs duringtransport.Casting process to take tundish baking， argon purged， add tundishcrystallization agent and carbon fluxes and other measures for the removal of inclusionshave a good effect.In RH refining process to increase the nitrogen content of thesharpest，alloy into nitrogen more.Steel slab tundish to a greater increase in the nitrogencontent.(3) From RH alloy after3min to casting billet steel inclusions mainly concentratedin0～3μm，the total amount of unit area of inclusions on the whole the trend wasgradually reduced，total reduction of16.95/mm2.More large-size inclusions in thetundish.RH and RH alloy after3min outbound inclusions in steel mainly Al2O3，as well as a small amount of MgO-Al2O3.Tundish inclusions mainly Al2O3，MgO-Al2O3.Slabinclusions mainly AlN，Al2O3，MnS.The average amount of slab inclusion of29.28mg/10kg， the number of large inclusions of6.79mg/10kg， inclusions are mainlyconcentrated in the0～50μm.Slab of large inclusions mainly Al2O3-SiO2，CaO-Al2O3-SiO2，CaO-MgO-Al2O3.(4)MnS, AlN can not be precipitated in the liquid phase and the phase，in theaustenite begins to precipitate, precipitation temperatures were1561K and1480K.MnSand AlN precipitation in austenite were critical nucleation size1.0nm～2.0nm and0.5nm～2.5nm.At the same temperature MnS and AlN dislocation nucleation criticaldimensions less than the critical dimension of homogeneous nucleation.MnS inaustenite uniform nucleation and dislocation nucleation maximum nucleation rate was1140K，1200K，the fastest precipitation temperatures of1220K，1210K.AlN in austeniteuniform nucleation and dislocation nucleation maximum nucleation rate was990K，1080K，the fastest precipitation temperatures are1090K.MnS and AlN bit wrong inaustenite nucleation rate is higher than the homogeneous nucleation，precipitation fasttime.