Optimization Of Composition Of Steel For ROF Furnace Inner Cover

The steel which used in the ROF furnace is a high chromium-nickel austenitic heat-resistant stainless steel.ROF furnace works in high temperature and reducing atmosphere for long-term,requiring it to have a good anti-oxidation and corrosion resistance at high temperature.In this paper,compared pre-service YUS701 steel plate,the YUS701 steel plate after 20850h use whose austenite grain seriously grow up,the grain boundary oxidation occurred,the room temperature intensity decreased,the dislocation density decreased,and the massive M23C6 phase precipitated in the grain boundary,while the elongated ? phase is precipitated in grain,leading to its room temperature strength,high temperature strength,plasticity and toughness decreased.The microstructure,precipitation behavior,mechanical properties and high temperature oxidation resistance at 1100 ? of YUS701 steel which used in ROF furnace were investigated by optical microscopy,scanning electron microscopy and energy dispersive spectroscopy,transmission electron microscope and X-ray diffraction,thermodynamic simulation,heat treatment experiments,oxidation experiments,The following conclusions were obtained,and get the following conclusions:1.The tested steel by adding V or W,the austenite grains become coarsely;while its mechanical properties did not significantly improve,or even slightly reduced.The grains of the tested steel with Nb are refined,and the steel has excellent mechanical properties at room temperature and high temperature.However,as the Nb content increases,the precipitation of the ? phase and the Z phase increases at 650 0 C,so the Nb content can be controlled at about 0.2 wt%.When the content of C is reduced from 0.09 wt%to 0.05 wt%,which facilitating the austenite grains refinement and grain homogenization and reducing the precipitation of M6C carbide and M2(C,N)phase.And the Ni content of about 14.00 wt%is conducive to further control of steel in the a phase,Z phase and G phase of harmful phase precipitation.The content of elements in ROF furnace steel after optimized are:0.05 wt%C,14.00 wt%Ni,0.2 wt%Nb,it is not recommended to add W,V.2.With the increase of the solution temperature,the grain size of the test steel seriously increased and the strength and hardness decreased,and the plasticity and impact toughness increased.Under the condition of satisfying the grain size requirement,the test steel has good comprehensive mechanical properties at 1070?.When the tested steel is holding for different times at 1070?,the austenite grains are gradually homogenized with the prolonging of the holding time.When the solution temperature is 60min,the carbonitride in the crystal is completely dissolved,and only a small amount of Cr-rich carbide precipitates in the crystal.The tensile strength and yield strength are 798MPa and 419MPa respectively,which meet the design requirements.3.Nb-containing steel test after 1100 ? capable of forming a stable oxide 100h oxide film,oxidation kinetics at various stages of instantaneous oxidation of the lowest rate,so that the best oxidation resistance.