Study On The Microstructure And Mechanical Properities Of The Novel High Silicon Ferritic/Martensitic Steels

Based on the chemical composition of the conventional9-12%Cr ferritic/martenstic steel,6type of novel high silicon ferritic/martenstic steels were developed through purifying melting and alloying design optimization. Also, EP823steel was smelted to be the comparator wih the6SIMP steels.The microstructure and mechanical properties of6SIMP steels and EP823steel was investigated. Further more, the high temperature oxidation resistance of T91steel. SIMP-5steel and EP823steel were studied comparatively.The effects of quenching temperature on microstructure and mechanical properties were studied, and based on this, the steels should be quenched at1050℃for30min and tempered at760℃for90min. Full martensite SIMP-5steel was obtained with excellent mechanical properties after this heat treatment. The yield strength was688MPa, and the tensile strength was893MPa. At the same time, the room temperature impact absorption energy was maintained at54J. The heterogeneous precipitation behavior due to exist of delta ferrite was studied. The effect of delta ferrite on mechanical properties was discussed.The high temperature oxidation resistance was analyzed and evaluated through the thermostatic oxidation experiment at the temperature of1050℃for lh,and at the temperature of650℃,800℃for500h. The results showed that the SIMP-5steel had the excellent high temperature oxidation resistance, and the addition of the silicon could significantly improve the high temperature oxidation resistance of the9-12%Cr ferritic/martenstic steels.